[R-390] Crystal Oscillator Identification .

[W4QG]

All,
Please excuse the somewhat off topic post.

I came across a pair of crystal oscillators at the Hamvention in a box 
of miscellaneous 390A parts.
Almost no information on the net about them except for a NSN number and 
they appear to be made by Collins. Similar to 390(A) oscillators but 
definitely not identical.Info I found on the net indicates the NSN was 
applied for in 1963.

NSN 5963-00-503-2533
Nomenclature on the module is:
"Crystal Oscillator Unit
506 2641 003
S.W.E G-573071
SERIAL NO 3515"

Whatever it is, it would appear at least a few thousand were made. I 
couldn't find any info on the next higher assembly. I do have pictures 
if anyone is interested.

Anyone have a clue what radio this is from?

Thanks!