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.

        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.

        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