This military version of the 51S-1 receiver is almost never seen on the used market.
Thank you, Dan! The seller claims that this radio is fully working with tubes replaced and has undergone a complete alignment. Hopefully, caps have been replaced as well.
I’ll admit: if I had the space, I would add this rig to my collection in a heartbeat, although I expect the price of this unit will far exceed my budget! It is a beauty, though.