This is a pair of NOS vintage RCA transformers from my Dad's extensive collection of broadcast and audio equipment.  One box was still sealed when I found them, and the other was opened.  I took out the transformer for pics, and observed the A7566 and the 949366-1 numbers on the transformer and wondered if my Dad mis-boxed it for some reason.  This made me curious enough to break the seal on the other box, and I discovered it was identical to the first so I'm confident that these are the correct transformers in the proper boxes.

I don't know any history or application for these, unfortunately.