This is a Collins 75S-2 receiver and it is operational.  Rumor is that only 300 or so were actually built. I have also read that Collins used a 75S-1 chassis to create the 75S-2. The receiver appears to be all original inside with no modification or tinkering. The electrolytic caps have not been replaced butthere is no appreciable hum. I did de-ox all switches and tube pins and tube sockets.  All tubes test good with my trusty Lafayette TE-50A. ( 🙂  ).  I did use it on 40 meter CW and 75 meter SSB and had no problem with distortion. I didnt have all the necessary test components to follow the alignment but it is better than when i received it. 

Ebay number: 115844412653

Links:

https://www.eham.net/reviews/view-product?id=14376

https://www.hug-a-bug.com/75S_2.htm