Pot Codes

[Voidoid56]

Pot codes... yeah, well... it's a bit of a black art, innit?

I'll share what I know... or rather what I think I know. It's basically all theories in the classic scientific sense, i e interpretations that seem to work and have yet to be disproven. Proof would be credible period documentation spelling it all out, but I've yet to see that, and I doubt we'll ever see that, frankly. I mean, we don't even know who the manufacturers were in most cases.

Most of what I have is based on the guitars that interest me the most, i e Greco Fender copies. Which is a good thing, since they more or less invariably have a plaintext month and year of manufacture in their serials, giving you a solid date to compare any pot markings to.

Anyway, first up:

The "YM X" codes seems to have been first interpreted by Burny enthusiasts, as an aid to dating unserialled instruments from the 80's and 90's. It also works fine with Grecos, which have them from about 1980. The earliest I've seen in Tokais have been 1982, and they seem to be in most guitars from about 1985-86 or so.
It's on pots with embossed markings, below the kOhm number (rarely, there's what appears to be a parts number instead, I've seen 504071, 504041, 50472 and 50442 so far).
The first character is the last digit of the year, the second one is the month (1 - 0, plus N for November and D for December). A space follows, then a letter, almost always K, but P turns up infrequently and I've heard V being reported as well. The meaning of the letter is unknown. Some sources claim that P is on push-pull pots, but this is clearly incorrect, since PP-pots are technically very different, with a large switch box (like the lower part of a mini toggle switch) attached to the bottom.
You see these in various guitars from about 1980 to at least 93-94, so there's an overlap. So, for instance, a 2 for the year could mean either 1982 or '92. In practice, that's seldom a problem, most guitars have construction tells that lets you tell the decades apart.


Late '81/early '82 Burny RLG-50. Visible codes are 18 for Aug '81 and 1N for Nov '81.



1985 Tokai TST-50, 56 for June '85.


Tokai PB-45, 26 for Feb 1982, with the very rare P code (and clearly no push-pull pots). This is one of the earliest instances of pots with these codes I've seen in a Tokai.


0D for Dec 1980 in a early'81 Greco SE. The D is easily mistaken for 0.


The "parts numbers" version of this code style. 504071 and -41 with 06 and 07 date codes in a 1990 Greco RG-950 Rickenbacker 360 copy.

 

[Voidoid56]

Next date code up:

The "vertical lines" code is found in Greco Fender copies from about 1977 to 1980, and no doubt in other guitars from that period as well. Not in Tokais, however, as far as I know. Please note that I'm not really up to speed when it comes to Tokai Gibson copies, though.

This code format has the month and year reversed compare to the YM X format: the month first, then the year. The months are also given differently than in YM X, using 1 - 9 for Jan - Sept, then J, K and L for Oct - Dec ( i e the 10th through 12th letter of the alphabet).
The month and year is followed by one, two or three vertical lines, and finally a 1 or sometimes another vertical line. The final digit is always in the same position, so if the vertical lines are fewer than three, there will be one or two spaces ahead of it.

I'm not sure if there is any practical need to find an interpretation for the vertical lines, but there is one that seems to fit rather well. It has to do with a Japanese tradition of dividing months into thirds, called jun. Two ten-day jun are followed by a third that's 8, 10 or 11 eleven days long depending on the month: upper, middle and lower jun.
Like I said, it sort of fits. Would you need to subdivide date codes into periods that short for QA purposes? Well, other manufacturers don't seem to have thought so... but then again, US manufacturers often dated their pots by the week (and still do, I think?).
Who knows? It's an hypothesis at least.


1977 Greco SE: 97 for Sept 1977, single vertical line, two spaces and a 1. Note the "parts number" above it. 7 or 4 in the penultimate position could differentiate linear and log pots, 4 is found on tone pots.


1978 Greco SE, K8 for Nov 1978. Two vertical lines, one space and a 1. These have the plaintext kOhm and log-lin info.



Mid-1979 Greco SE-800, one pot is February with two lines, the other March with one line. The final digit has no clear "hook" to indicate that it's a 1.



Nov 1979 Greco SE600J. Semi-obscured, but we see the J in use for October and at least one vertical line.

 

[Voidoid56]

The rubber stamp code is a fairly early one, used in Grecos from at least 1974 up until 1976 or possibly into '77, and I've personally seen them in Heerby's as well. It might have been used significantly earlier than this as well, but so far, I haven't really looked that far back much.

It's stamped, not embossed, but seems conceptually similar to the vertical lines code: it's month first then year, and it uses J, K and L for Oct-Dec. But it has no vertical lines, instead, the M and Y characters are followed by a 1, a 2 or a 3, so whatever it indicates it could be the same as the lines. The final character is an underlined letter of unknown meaning. I haven't really paid much attention to it, but I found A, B, H and I when I looked through my own pics. This format also uses part numbers and plaintext tech info interchangeably.


1976 Greco PB-700. Dec '75 and Jan '76 codes and parts number stamps.


1976 Heerby SG-480. All four pots are March '76, plaintext tech info.




1976 Greco TE-500. Oct 1976, parts number.

 

[Voidoid56]

And there are other recurring pots with markings as well. One type is the J NOBLE pots, often seen in Fernandes RST's and other Revivals, from about 1982 and into the 90's. Infuriatingly, they have markings than not only seems undeciperable but are also really hard to se. They're on the edge of the pots, not the bottom, with the interesting bits facing the solder lugs, often being obscured by cables and general clutter.

The markings say "J NOBLE" (which I assume is a brand name), then often (but not always) 15, the comes the tech info. then, just above the middle solder lug, some potentially interesting bits that makes no sense afaik: A8P, A8Y, bY, bS... it doesn't seem to connect to any obvious time-telling system. Mysterious stuff.





It's all BS to me...


One little oddity with Fernandes' use of the pots in Strats: they're all "long-stemmed", not your typical short Strat pots. An extra nut is used as spacer.