Old date codes

[Old_School]

Does anyone have info on early tube date codes? I've been able to find a bit, mainly the really big names in tube manufacture, but most of the internet info is post-War (that's WWII in case anyone is wondering which war).

I have a pair of Ken-Rad tubes with date codes K5E. From what I could find, a code like that is the same as RCA codes pre-War and through the War. A K5 code indicates 1943 Sept-Oct delivery. E would indicate either an OEM product or a tube provided for government.

What I've also been able to find is that Ken-Rad was independent 'till '45/'46 when it was bought out by GE. However, there was quite a bit of "cross-pollinization" back in the day, with some companies doing OEM for others.

 

[mhardy6647]

There's a good book by Ludwell Sibley called Tube Lore.
Looks to be out of print now, though.

 

[spaceman]

Where did you find info for dating Ken-Rads? I have a couple Ken-Rad 6V6 variants in my SE amp, & knew they were "kinda" old, but never tried dating them. :scratch2:

 

[spaceman]

Where did you find info for dating Ken-Rads? I have a couple Ken-Rad 6V6 variants in my SE amp, & knew they were "kinda" old, but never tried dating them. :scratch2:

EDIT: BTW, I think GE just bought them out for their EIA code.

 

[Old_School]

Where did you find info for dating Ken-Rads? I have a couple Ken-Rad 6V6 variants in my SE amp, & knew they were "kinda" old, but never tried dating them. :scratch2:

I googled a lot. I ended up finding a .pdf of RCA date codes which matched the pattern, but if they are correct is anyone's guess. I emailed a couple of tube gurus (Jim McShane and Damon Coffman) but neither knew the codes, though Damon said the Ken Rad are great tubes.

Now I'm not sure what the point of dating them is anyway. If they test good, and sound good in an amp (which I don't have at the moment), I'll be a happy man.