I made a start on cleaning all the dust out of my Masco ME-27 the other day and I noticed that both the 6L6Gs were branded "Masco".

I assume that they were actually made by one of the big manufacturers, but is there a way to tell which one?

As to the second part of the question in the title, I suspect that the answer may be "No" but, as always, am happy to be corrected.

What letters or numbers are on the tubes? Maybe some mfr. codes... maybe not.

As to whether it matters, that depends on you. Some of the audio folks can tell the difference in the way tubes "sound." I can't.

Rich

I personally think that it matters because they are historically accurate. I would not change them for a different brand. That's just my opinion.

No doubt were mfg'd by someone other than Masco...

There is almost always a mfgr ID code on tubes, I have a pair of Harman Kardon 6L6GC that have GE's 188 code on them...

Tom

Funny you should say that, Tom. I popped the lid off and had a look - the code on all the "Masco" tubes is 57-13 / 188-4 (two 6L6Gs and a 6SC7 - the others are branded GE & Philco, so have presumably been replaced since manufacture).

So, if 188 means GE, would 57 be the year? If that's right, presumably the 13 is a date code (13th week?) but what's the 4 - a plant ID?

I know I could google this, but guessing's more fun.

You have it exactly correct 188 = GE, year '57, week 13 and plant code... GE is the only one I can think of that used a plant code, otherwise it's a std code system(with decade variations) put in place after WWII...

A few other codes are RCA 274, Sylvania 312, Tung-Sol 322, Raytheon 280, Amperex 111...

Tom