The parts
THE PARTS
The hidden architecture of a vintage humbucker
A vintage PAF is often described in remarkably simple terms: two coils, a magnet, some screws and a cover.
That description is technically correct — and completely misses the point.
A vintage humbucker is an assembly of magnetic materials, conductive materials, plastics, wood, steel, brass, insulation and mechanical components, all manufactured with the tooling and tolerances of their time.
The interesting part is that many of these components were never designed to be “tone components”. They were simply the materials Gibson could source, the machines it had available, and the parts that could be manufactured economically in Kalamazoo.
And yet, decades later, those details have become part of what makes an original PAF so difficult to reproduce convincingly.
The real fascination is not that one particular component is magical.
It is that the entire system is historically coherent.
01 — THE BOBBINS
The two coil bobbins are the foundation of the humbucker.
One carries the fixed steel slugs.
The other carries the adjustable pole screws.
The coils are wound directly around these plastic forms, and almost every subsequent component interacts with them.
During the PAF era, Gibson bobbins were moulded from cellulose acetate butyrate (CAB), commonly referred to simply as butyrate.
This is an important distinction because modern reproduction pickups frequently use ABS.
Butyrate vs ABS
Butyrate and ABS are not the same material.
Cellulose acetate butyrate is an older cellulose-based thermoplastic. It has a different mechanical behaviour from ABS and can be somewhat softer and more flexible.
That matters because the enormous number of turns wound around a bobbin places mechanical stress on the plastic.
Vintage butyrate bobbins can therefore show:
slight deformation
subtle bowing
mould imperfections
burrs around moulded openings
uneven edges
small differences between mould cavities
surface changes caused by age
These aren't necessarily defects.
They are part of the manufacturing fingerprint.
Later Gibson humbuckers moved toward different plastic formulations, including ABS, which is mechanically different and generally more dimensionally stable. The distinction between vintage CAB/butyrate and later plastics is therefore important when reproducing a specific period.
02 — THE FAMOUS “CIRCLE IN A SQUARE”
One of the most recognizable details of a PAF bobbin is the small square opening surrounded by a circular mould impression.
Collectors often call it:
“square in circle”
or
“circle around the square.”
It is not decoration.
It is a consequence of the moulding and ejector/tooling arrangement used to manufacture the bobbins.
The original moulds were made specifically for Gibson's humbucker production, and surviving bobbins can contain mould identifiers and cavity-related details.
The detail is particularly useful because reproductions often imitate the general appearance but miss the subtle geometry.
The original parts are not perfectly geometric.
The circles aren't always perfectly crisp.
The edges aren't always perfectly clean.
And that is precisely what makes them interesting.
03 — TOOL MARKS
If you want to understand vintage Gibson construction, tool marks are almost as important as the nominal specifications.
A modern reproduction can have:
the correct magnet
the correct wire
the correct bobbin colour
the correct resistance
…and still look completely wrong under magnification.
Why?
Because the original tools left fingerprints.
The “L” marks
Vintage Gibson humbuckers are known for characteristic L-shaped tooling marks on the baseplate feet.
These marks are manufacturing traces, not decorative features. They can be visible on PAFs and early Patent Number pickups and gradually become less common as tooling and production methods evolved.
Their presence can therefore provide useful historical information.
But they should never be treated as a simple:
L mark = PAF
rule.
Gibson production changes were gradual, inventories overlapped, and old components could remain in use after a new part had been introduced.
That is one of the recurring themes of vintage Gibson archaeology:
transitions rarely happen on January 1st.
04 — THE BULLSEYE SLUGS
Another spectacular detail is found on the fixed pole pieces.
Look closely at the top of an original PAF slug and you can sometimes see concentric machining rings.
These are commonly called:
bullseye marks.
They are the visible result of machining the steel slug.
The slug is not simply a perfectly polished cylinder.
The machining process itself can remain visible on its upper surface.
These marks became one of the visual fingerprints associated with vintage PAF construction.
And again, the important point is not simply whether a bullseye exists.
The exact appearance can vary.
Some vintage parts show strong concentric rings.
Others show much subtler machining.
Transitional parts can also exist.
That makes the bullseye an excellent example of something that is useful for authentication and historical interpretation, but dangerous when turned into an absolute rule.
05 — THE SLUGS
The fixed pole pieces are steel.
They sit inside one bobbin and conduct magnetic flux from the Alnico bar toward the strings.
Their dimensions, steel composition, machining and plating all matter mechanically and magnetically.
Specialist analysis and reproduction work frequently emphasizes the importance of the steel's carbon content. Low-carbon steel was used for important magnetic components of vintage PAF construction, and the metallurgy of these parts affects their magnetic behaviour.
The original parts also show machining fingerprints that modern manufacturing often removes.
That distinction is important.
A perfectly machined modern slug can actually look less vintage than an imperfect old one.
06 — THE POLE SCREWS
The other bobbin carries the adjustable pole pieces.
These are generally 5-40 Fillister-head screws in the classic Gibson design. They are steel and were nickel plated or gold plated depending on the pickup's finish.
The screw geometry is surprisingly important for an accurate reproduction:
head diameter
head height
slot geometry
thread
shaft diameter
plating
machining marks
relationship between screw and bobbin
The slot itself can tell a story.
Vintage screw slots are not necessarily as perfectly uniform as modern CNC-produced parts.
07 — THE KEEPER BAR
Hidden underneath the bobbins is one of the least visible — and most important — pieces:
the keeper bar.
It is a steel component positioned alongside the Alnico magnet.
Its job is to form part of the magnetic circuit and provide the magnetic path between the magnet and the pole-piece assembly.
The pole screws pass through it.
According to specialist documentation, vintage Gibson keeper bars have been associated with cold-rolled 1016 steel, although exact material specifications should not be assumed for every individual vintage pickup.
The keeper is a perfect illustration of the 59DNA philosophy:
A part you cannot see can still be part of the sound.
08 — THE MAGNET
The magnet is the heart of the magnetic circuit.
Classic Gibson humbuckers used a single Alnico bar magnet.
The term Alnico refers to an alloy family principally based on:
Aluminium – Nickel – Cobalt
with iron and other elements forming the remainder of the alloy system.
But saying:
“It's Alnico II”
doesn't tell the entire story.
The magnetic behaviour also depends on:
alloy composition
orientation
casting/manufacturing method
heat treatment
charging level
magnetic history
ageing
geometry
Gibson's vintage magnets were not all identical.
Historical research has documented Alnico II, III, IV and V in vintage PAF discussions, with Gibson's own analysis finding a notable incidence of Alnico III in a small sample, despite records indicating orders for Alnico II.
That alone should make anyone suspicious of statements such as:
“Every 1959 PAF had Alnico II.”
Vintage production simply wasn't that clean.
09 — MAGNET LENGTH
Magnet geometry also changed.
Early PAF-related magnets were approximately:
2.5" × 0.5" × 0.125"
Later, Gibson transitioned to shorter magnets, around 2.25–2.31", depending on the period and source.
This change is important because shortening the magnet changes the magnetic circuit.
It is therefore not merely an external dimensional detail.
A shorter magnet can produce a different distribution of magnetic flux through the keeper, slugs and screws.
Again:
geometry is part of the material.
10 — ROUGH CAST vs GROUND
Vintage magnets can show a distinctly rough, irregular surface compared with modern precision-ground magnets.
This is another place where reproduction philosophy matters.
A modern manufacturer might instinctively think:
“Make the magnet perfectly smooth.”
But historical accuracy may require the opposite.
The visible surface of a vintage magnet can retain traces of its manufacturing process.
Those marks are not necessarily important because they magically affect tone.
They are important because they tell us:
how the part was made.
11 — THE COIL WIRE
Now we reach one of the most important components of the pickup:
the wire itself.
Classic PAFs used approximately 42 AWG copper magnet wire, with plain enamel insulation.
42 AWG is extremely fine wire.
The conductor is only around 0.063 mm in diameter before accounting for insulation.
And thousands of turns are required for each coil.
The insulation is therefore not a trivial detail.
12 — PLAIN ENAMEL
Plain enamel is an old insulation system.
Vintage Gibson wire is often visually associated with a dark:
purple / maroon / reddish-brown
appearance.
That colour is particularly noticeable when looking through the small opening in a vintage bobbin.
Historical examples show changes in wire appearance through the 1960s, including the transition toward brighter orange/red wire in later Gibson production.
But colour alone is never enough to date a pickup.
Age, lighting, varnish, oxidation and photography can all change what the wire appears to look like.
13 — PLAIN ENAMEL vs POLYURETHANE
This distinction is crucial when building a vintage reproduction.
Modern polyurethane/poly-coated wire can have:
different insulation thickness
different mechanical properties
different stripping behaviour
different overall coil dimensions for the same conductor gauge and turn count
The insulation contributes to the total diameter of the wire.
That means:
same AWG ≠ same finished coil.
Two wires can both be called 42 AWG while producing different coil dimensions because their insulation systems differ.
The wire therefore needs to be considered as a complete system:
conductor + insulation + diameter + tension + winding geometry.
14 — THE NUMBER OF TURNS
A PAF coil is often described as having approximately 5,000 turns.
But this should not be treated as a rigid specification.
Vintage winding machines and production practices produced variation, and early machines could lack automatic stopping systems. The operator could therefore stop the machine when the bobbin was judged to be full.
The result?
Two coils from the same production period can have different:
turn counts
wire lengths
DC resistance
inductance
capacitance
physical coil dimensions
That variation is part of the historical reality.
15 — THE BOBBIN LEADS
Each coil needs to connect electrically to the pickup's external wiring.
Vintage Gibson construction used short internal coil leads, historically seen in different colours and configurations as production evolved.
Early examples commonly show black leads, while later production moved toward combinations including black and white.
These tiny pieces of wire are another excellent dating clue.
And they are almost invisible once the pickup is assembled.
16 — THE BASEPLATE
The baseplate is the mechanical foundation of the humbucker.
The bobbins, keeper bar, magnet and mounting hardware all ultimately relate to it.
Vintage Gibson PAF baseplates were made from German silver, also called nickel silver — a copper-based alloy containing nickel and zinc.
Despite the name:
German silver contains no silver.
Its relatively low electrical conductivity compared with pure copper is useful in pickup construction, particularly for covers and related components.
The baseplate also carries many of the visual fingerprints collectors use:
leg length
screw type
stamping
tool marks
plating
solder joints
hole geometry
17 — THE ALLOY MATTERS
One of the biggest mistakes in modern reproduction is treating metal simply as:
“steel.”
Steel is not one material.
Its composition can vary dramatically.
Carbon content, alloying elements, processing and heat treatment can all change:
hardness
permeability
machinability
magnetic behaviour
surface finish
response to plating
Specialist pickup builders have long experimented with different low-carbon steels for slugs, screws and keeper bars for precisely this reason.
So when reproducing a vintage pickup, saying:
“steel slug”
is only the beginning.
18 — BRASS SCREWS
The small screws holding the bobbins to the baseplate were generally brass in classic Gibson construction.
Brass is essentially a copper-zinc alloy and is non-ferromagnetic.
These screws are often overlooked because they are hidden underneath the pickup.
But again, the philosophy is simple:
the original pickup was assembled from a specific collection of materials.
Replacing every screw with generic modern steel changes that system.
19 — THE WOODEN SPACER
Between the magnetic assembly and the bobbin structure is another easily overlooked component:
the spacer.
Classic PAF construction used hard maple spacers in the magnetic assembly.
The spacer provides mechanical support and establishes the correct relationship between:
magnet
keeper bar
bobbins
baseplate
Later Gibson designs changed spacer materials, making the spacer another useful period clue.
The early combination of:
wood + Alnico + steel + butyrate
is part of the physical architecture of the classic PAF.
20 — THE TAPE
The coils themselves are wrapped in insulating tape.
This tape is there primarily to:
protect the winding
hold the coil together
isolate the wire
provide mechanical stability
keep the winding from being damaged during assembly
Vintage Gibson examples show different tape characteristics through the years, including changes in colour and material. Historical examples have been documented with dark olive tape in earlier production and black tape later on.
The tape is therefore another apparently insignificant component that can become highly informative when examining an original pickup.
21 — THE LEAD WIRE
The pickup's external lead is another important part of the construction.
Classic Gibson humbuckers used a single-conductor braided shield lead.
Inside:
central conductor → coil connection
Outside:
braided metal shield → ground
The braided shield provides both electrical shielding and the characteristic vintage appearance.
The early black cloth-covered conductor and braided shield are particularly recognizable on vintage Gibson pickups.
Later construction details evolved, but the braided lead remains one of the most recognizable features of a vintage Gibson humbucker.
22 — THE COVER
The cover isn't simply cosmetic.
The earliest humbuckers used brushed stainless-steel covers, before Gibson moved toward nickel-silver construction.
Classic nickel covers were made from nickel silver and plated with nickel.
Gold versions were generally gold plated over nickel.
This creates an interesting visual effect on heavily worn examples:
gold → nickel → underlying metal
as the plating wears.
The covers were also relatively thin.
That matters because any conductive metal surrounding a pickup can interact electromagnetically with the pickup's field and eddy currents.
This is one reason the material, thickness and construction of a cover are not completely irrelevant to the electrical behaviour of the pickup.
23 — THE COVER IS NOT JUST A COVER
A vintage cover changes the electrical environment of the pickup.
It can influence:
high-frequency response
resonance
Q factor
eddy-current losses
The exact magnitude depends on:
alloy
thickness
plating
geometry
distance from the coils
grounding
This is one reason an uncovered pickup and the same pickup with a vintage-style cover can sound measurably different.
24 — THE M-69 RING
Although technically outside the pickup itself, the M-69 mounting ring belongs in the same historical ecosystem.
These rings were injection-moulded components with their own tooling history and markings.
The moulds themselves can leave identifying details on the underside.
Even the machining/cutting operations used during production could leave characteristic marks.
The M-69 is another excellent reminder that Gibson's vintage parts weren't anonymous pieces of plastic.
They were products of specific moulds, cavities, tools and production decisions.
25 — BLACK, CREAM, ZEBRA
The famous bobbin colours were not originally created as tonal options.
They were largely a consequence of manufacturing and supply.
PAF bobbins were normally black, but cream bobbins began appearing around 1959, producing:
double black
zebra
double cream / double white
configurations.
Guitar World notes that cream bobbins appeared because of supply issues, and that the colour itself has no reason to alter pickup output.
This is an important distinction.
The mythology surrounding rare double-white PAFs is enormous.
But:
rare ≠ acoustically superior.
The rarity is primarily historical and collectible.
26 — BUTYRATE AGES DIFFERENTLY
One of the reasons collectors love old Gibson plastics is that they age.
Butyrate can develop:
colour changes
translucency
surface oxidation
shrinkage
deformation
stress marks
The plastic can also interact visually with decades of exposure to:
ultraviolet light
heat
humidity
sweat
solvents
storage conditions
Consequently, two originally identical bobbins can look quite different sixty years later.
That is why reproducing an aged appearance is considerably more difficult than simply choosing:
“vintage cream.”
27 — ABS IS NOT “BAD”
ABS deserves a fair treatment.
ABS is a very useful engineering plastic.
It is:
strong
stable
easy to mould
dimensionally consistent
widely available
And it is perfectly capable of making an excellent pickup.
The problem only appears when the goal is:
historical reproduction of a specific vintage Gibson.
If the original part was CAB/butyrate, an ABS reproduction is mechanically and materially different.
If the objective is simply a reliable modern pickup, ABS may be perfectly appropriate.
If the objective is:
1959 PAF reconstruction
then material history matters.
28 — WHY TOOLING MATTERS SO MUCH
This is perhaps the most important principle of THE PARTS.
A modern part can reproduce the nominal dimensions of an original while still being fundamentally different.
Imagine two bobbins:
Bobbins A
correct dimensions
correct colour
correct hole spacing
perfect surface
CNC precision
Bobbin B
correct dimensions
original mould
slight burr
subtle radius variation
tiny ejector mark
slight deformation
period-correct plastic
On a specification sheet:
almost identical.
Under a microscope:
completely different manufacturing histories.
That is the difference between reproducing a part and reproducing a manufacturing process.
29 — THE PARTS WORK TOGETHER
A pickup does not hear the magnet.
It does not hear the wire.
It does not hear the bobbin.
It responds to the electromagnetic system created by all of them together.
The magnetic circuit is approximately:
Magnet → Keeper → Slugs / Screws → Strings → back through the magnetic circuit
while the electrical system is determined by:
Copper wire + resistance + inductance + capacitance + load
and the mechanical system includes:
Bobbin + winding + tape + baseplate + magnet + keeper + screws + cover
These systems interact.
30 — WHY WIRE AND BOBBIN GEOMETRY MATTER
Two pickups can use:
the same 42 AWG wire
the same magnet
the same bobbins
approximately the same DC resistance
…and still not be electrically identical.
Why?
Because resistance only tells you part of the story.
The physical distribution of the wire changes:
total wire length
average turn length
coil geometry
distributed capacitance
inductance
resonant frequency
Q factor
This is where THE WIND and THE PARTS meet.
The material tells us what the wire is.
The winding process tells us where the wire goes.
31 — THE PAF AS A SYSTEM
A historically convincing PAF therefore isn't simply:
Alnico II + 42 AWG + 8kΩ.
That is an oversimplification.
It is closer to:
Alnico alloy
magnetic charge
magnet geometry
steel composition
keeper geometry
slug machining
pole screw geometry
German-silver baseplate
butyrate bobbins
42 AWG insulation system
winding pattern
coil tension
turn count
coil mismatch
wood spacer
tape
lead wire
cover
assembly tolerances
That is a much closer description of the real object.
32 — WHY TWO ORIGINAL PAFs CAN BE DIFFERENT
This is perhaps the most fascinating part.
Two original PAFs from the same year can differ.
Not because Gibson deliberately created different “models”.
But because industrial production contains variation.
Different:
magnet batches
magnet strength
wire batches
bobbin mould cavities
machine settings
winding machines
operator decisions
steel batches
machining tolerances
component inventories
could all contribute to differences between individual pickups.
Historical sources specifically document variation in winding, materials and construction throughout the PAF period.
That is why the idea of a single, mathematically perfect “1959 PAF specification” is misleading.
There was never just one.
33 — THE REAL VINTAGE FINGERPRINT
When you look inside an original PAF, the most interesting things are often the things Gibson never intended anyone to admire:
a machining ring on a slug
a slightly imperfect mould cavity
an L-shaped tool mark
a small difference between two bobbins
a piece of maple
a slightly uneven magnet
a particular wire colour
a brass screw
a solder joint
a tiny difference in coil geometry
a piece of tape
Individually, none of these components explains the sound of a PAF.
Together, they describe how the pickup came into existence.