IBM vacuum tubes

[Guy N.]

On Tue, 2020-06-16 at 11:04 -0400, William Donzelli wrote:
> > Good question.  They have an IBM logo and "Made in USA", along with the
> > part number (5965 or 5963) and a bunch of numbers that might give a hint
> > as to manufacturer.  Any suggestions on how to decode them?
> 
> What are the numbers?
> 
> Details, man!

Sure!  I'd attach a picture, but....

On the top of the tubes are numbers printed in yellow.  A couple typical
ones are C392 and C152.

On the side, the large IBM logo is flanked by groups of numbers, an
example:

62-39  64-17   IBM     317261
       188-5          MADE IN U.S.A.

This is one of the more legible ones.  The two pairs of numbers on the
first line at the left appear to vary, the 188-5 and 317261 seem to be
constant; but it's hard to be certain.

The obvious part number 5965 has some other markings that are
overprinted by the IBM logo and numbers.  It looks like it could be:

   5965
    A
   U.S.A
    ..
    ..

The pattern of dots is hard to make out because of "IBM" on top of it.

The structure inside is a "long-plate" type, with three horizontal ribs.
I haven't had a chance to compare the structure to any of the many old
dual-triode, medium-mu tubes in my assortment.  There might be some
clues.  It wouldn't surprise me if these were a fairly standard design
with some changes to the cathode to withstand being held in cutoff for
long periods of time.