A detail often overlooked and seldom known about vintage Fender potentiometers important to authenticating a vintage guitars components is the Fender factory part code stamped onto the pots beginning in 1958 and used consistently to date.
There is evidence the parts code was started in late 1958-early 1959 on Jazzmaster pots. This year tends to have an 4-digit code. The codes were gradually applied to other models and by mid 1962 all pots were coded and the digits increased to 10 digits. This system gave same or similar part numbers on both CTS and Stackpole pots until the CBS takeover. When this happened the part numbers were reduced to 6 digit numbers that usually correspond to the parts lists. To demonstrate, I will use the Telecaster potentiometer to show the evolution of the part code.
1958 Telecaster Potentiometer
Manufacturer and Date code* Part Number
137-825 3596
304-6103 220072-46
304-6235 70-2125-0034
304-6350 70-2125-0034
304-6423 70-2125-0034
137-6534 70-2125-0034
137-6622 032367
304-6622 032367
304-7306 032367
137-7352 032367
*-304 is Stackpole and 137 is CTS
The code changes somewhere between 1965 and 1966. I believe there is most likely a transition between the two codes during mid-late 1965. It was also during this time Fender began using CTS pots heavily and from what I have seen with other models, the code change was started with the CTS brand then the Stackpoles changed to follow suit.
Okay, now that I shown the theory, I will show some deviations with the code. Lets take "032367" as an example. In theory, this code represents a solid shaft, 250K ohm potentiometer used in Telecaster, Esquire, Musicmaster family, P-Bass, J-bass , Bass 6, and any other guitar requiring a pot with these specs. Often amplifiers require a similar potentiometer in the circuit. I have seen many 032367 pots in late 60's and 70's amplifiers. Usually they have a nylon shaft, but these are found in guitars as well from time to time. I have found 250K audio taper solid shaft pots in amps coded 021840 and 021857. I presume that these pots vary in specs due to having custom tolerance specifications, reverse taper, or wattage ratings designed specifically for amplifiers. I have never seen these codes in a stock Fender guitar.
Non-guitar use pot found in amplifiers:
302-6206 70-2125-0012
302-6223 70-2125-0012
302-6426 70-2125-0012
304-6521 032367
304-6614 021857
I should also mention the 1966 dated pots. CBS Fender bought a huge surplus of pots in 1966. You can find 1966 pot codes, especially on 250K solid shaft pots, well into the early 70's. These pots can usually be found in Telecaster, P-Bass, J-Bass, Steel, amplifier and Mustang guitars. In his book, Forrest White claims after he left Fender the (untrue) rumor went around he was fired for buying up items in surplus. These pots are perhaps an example of that made the rumor believable to insiders.
Mexico stamped pots- I often encounter questions about seemingly original pots from the early 70's with a "Made in Mexico" stamp on them, with correct year code and even correct part number. It seems that CBS atleast ordered components from Mexico in the early-mid-70's. Maybe it was an attempt to save some money, maybe the US suppliers were running a backlog, I am not sure what the truth is. One amp historian claims that in this timeframe Fender outsourced a bulk of their handwiring to Mexico. It can be assumed fender either went in and bought some components from the area to be used in the US or maybe Fender even experimented with having pickguards wired in Mexico. Hopefully this will be answered someday.
Here is a table of some of the other model codes I have found. If you have any you would like to share from your guitar or amplifier Click Here .
Other models:
Stratocaster:
304-6306 Part # 70-2125-0035
304-6545 035865
304-6628 035865
137-6650 035865
137-7212 035865
137-7807 035865
137-8623 013446
Jaguar/Jazzmaster:
Rhythm thumbwheel pots:
50K 304-6303 #70-2488-0281
1 Meg 304-6321 70-2488-0282
50K 137-6619 015511
1Meg 137-6619 015529
1 Meg CTS 0017 (17th week of 2000) 054457
Master controls:
1 Meg Linear (Jazzmaster Volume) 137-5906 3495
1 Meg Audio (Jazzmaster Tone) 137-5906 3494
1 Meg Linear (Jazzmaster volume) 304-6237 70 2135-0125
1 Meg Linear (Jazzmaster volume) 137-6350 70-2125-0125
1 Meg audio 304-6450 70-2125-0240
1meg linear 137-6615 015453
1 Meg audio 137-6606 015479
1970's Stringmaster steel
Volume and tone 250K 304-7205 032367
Blend 250K 304-6612 015487
24
Becker
34 Cornell-Dublier
67 Eminence
101
Admiral
106 Allen-Bradley
117 Credence Speakers
119
Automatic Manufacturing
124 Alpha Wire
125 Bendix
130
Matsushita/Panasonic
132 Talk-A-Phone
134 Mepco/CentraLab/NA Philips
137
CTS
140 Clarostat
145 Cinaudagraph/Consolidated
145
Illinois Capacitor
150 Crescent
169 Hitachi
185
Motorola
188 GE
213 Dearborn Wire
220
Jensen/Viking
232 Magnavox
235 North American Capacitor
245
National
251 Omite
252 DuKane/Operadio
260
Philco
270 Quam-Nichols
274 RCA
277
Emerson/Radio Speaker
280 Raytheon
285 Rola
286
Ross
296 Solar
304 Stackpole
308
Stromberg-Carlson
312 Sylvania
322
Tung-Sol
328
Utah/Oxford
336 Western Electric
343 Zenith
371
Best
381 Bourns
391 Altec-Lansing
394
Foster Transformer
416 Heath
433 Cleveland
449
Wilder
465 Oxford/McGregor
466 Delco
549
Midwest
575 Heppner
579 Belden/Cooper
589
Bogen
649 Electro-Voice
706 Pioneer
719
Carbonneau
736 Sprague/Allegro MicroSystm
742 Esquire
748
Russell
756 Universal
767 Quincy
787
Sonatone
789 McGregor
794 Harmon Kardon
795
Atlas
828 Midland
840 Ampex
847
University
918 Oaktron
1056 Fisher/Gefco
1059
Channel
1098 Pyle
1113 Acoustic Fiber Sound
1149
Curtis Mathes
1191 Micro Magnet