Diagram showing how to read an EIA potentiometer code: 137 is CTS, 65 is the year 1965, 42 is week 42

How to Date a Guitar by Its Pot Codes (and What the Date Can't Tell You)

October 17, 2026

Short answer: the numbers stamped on the side of a volume or tone pot are a date code. Read them and you get the rough week and year the pot was made, which tells you the earliest the guitar could have been assembled. They are one of the best cross-checks for "is this electronics cavity original?" on a used Gibson, Fender or PRS, as long as you treat the result as a clue and not a verdict.

What a pot code is

Most American-made pots from the mid-century onward carry an EIA source code: a six- or seven-digit number stamped on the metal body. The first three digits identify the manufacturer. The rest give the date. Collectors lean on it because a guitar's serial number can be ambiguous (Gibson's older numbering is famous for it), while the pots inside carry their own timestamp.

How to read one, step by step

1. Find the maker

The first three digits name the manufacturer. The one you will see most often is 137, CTS (Chicago Telephone Supply). One pot-code reference I checked also lists 134 as Centralab, 304 as Stackpole, 106 as Allen-Bradley, 140 as Clarostat and 381 as Bourns. IRC used a different system, so its codes do not follow the standard reading below. I could only cross-confirm CTS = 137 across multiple sources, so treat the rest of that list as a good starting point rather than gospel.

2. Split the date

What is left is either three or four digits. With four digits, the first two are the last two digits of the year and the last two are the week. So 137 6542 is a CTS pot from week 42 of 1965. With three digits, the first is just the last digit of the year and the last two are the week.

3. Deal with the decade problem

A three-digit date only gives you one year digit, so the decade is a guess: 137 842 could be 1948 or 1958. Three-digit codes show up mostly on 1940s and 1950s parts, and four-digit codes take over in the 1960s and later, so context usually settles it. If the week digits come out above 52, it is not a source-date code at all.

What the date does and does not tell you

This is where people get burned. A pot code dates the pot. Manufacturers often stamped parts weeks, even many months, ahead of when they were used, so the code gives you the earliest possible build date, not the exact one. On a healthy original guitar I expect the pot dates to land a little before the serial or neck date, and a few months of gap is normal. A gap of a year or more is a prompt to look harder: is the neck original to the body, or have the pots been swapped?

The reverse is the red flag that matters more. If the pots are newer than the guitar's claimed year, something has been replaced. That is not automatically bad, since plenty of good guitars have had a worn-out pot swapped, but it changes how I price the guitar and what I say about it. For a deeper look at that, see how to tell if a used guitar's electronics have been replaced.

How to check without wrecking anything

Look first, unsolder never. The code is usually on the side or back of the pot body. On a Les Paul or SG that means pulling the control cavity cover. On a Strat it usually means lifting the pickguard, which is easy to do carefully. Do not unsolder wires just to read a code.
Read more than one pot. Codes are often partly hidden under solder, so assemble the date from two or three pots. They should agree with each other within a few months.
Check the other clues. Compare against the serial number, the neck date on a Fender, and the overall spec. Our guides on dating a used Gibson by serial number and dating a used Fender by serial number and neck date cover those.
Match the maker to the era. If the code does not fit the period, or the pots look newer than the wiring around them, assume replacement until proven otherwise.

My honest take: how much weight to give it

I use pot codes as a tiebreaker, never as the main evidence. They are brilliant when a serial number points to two possible years, and they are a fast way to spot a rewired guitar. But a single code does not prove authenticity or originality, and replaced electronics, factory parts changes and decades of repairs can all muddy the picture. Original electronics do generally matter to collectors, so a consistent set of period-correct codes is a real plus. A missing or mismatched set is a reason to ask questions, not to walk away.

One caution on newer guitars: many modern import pots do not use the classic EIA scheme, and in my experience they are often harder to date, so do not assume every pot you see will decode. If you are not sure what a stamp means, treat it as unknown rather than forcing a reading.

If you are weighing what a guitar's originality means for value, our Cash Offer page is the quickest way to see what we would pay for yours, and if you are shopping, the guitars in stock are all inspected and described in detail, including the 2023 Les Paul Standard '50s in Honey Amber currently on the shelf.

FAQ

Can a pot code tell me the exact year my guitar was made?

No. It tells you when the pot was made, which is the earliest the guitar could have been built. Parts are often dated weeks to months ahead of use, so the real build date is usually a bit later.

What does 137 mean on a guitar pot?

137 is the EIA manufacturer code for CTS (Chicago Telephone Supply), the most common pot maker you will find in American guitars.

My pot has a three-digit date. How do I know the decade?

You cannot from the code alone. Use context: the guitar's serial number, its features, and whether the maker was using three-digit or four-digit codes in that period. Three-digit codes were mainly a 1940s and 1950s habit.