ID Mod Transformers

[John K5PRO]

I have two Collins Mod Transformers, one from EPAY and another from a local SK's junkbox. Turns out these are the same beast, just different packaging and vintage. I need help identifying what they came out of. Must be something common, because the guy on EPAY was selling a collection of them one at a time, months ago. Then I found this one in town.... They are a little large to use in a DX100 or Apache.Thanks for any advice:
 
Three secondaries, 50 VCT, 600 Ohms CT and 2400 Ohms/350 mADC
Primary unmarked impedance, with CT
Response 200-15000 Hz +/- 1 dB
Both are 4.25 x 4.75 x 5.5 inches high approx, hermetically sealed with 11 terminal studs underneath (12 would be a perfect 4x3 rectangular cluster, one corner doesn't have a stud for 11)

Collins 677-0388-00
Flanged base,  paint is light olive
"CHICAGO TRANSFORMER
3 kV Test"

Collins 677-0525-00
Studs on base, paint is black
"CHICAGO STANDARD TRANSFORMER 18075
1425 PWV"