I have an APR-4Y, the postwar version with the miniature tubes and the multiband tuning unit.  I have yet to fire it up; I'll need to build a power supply, the original 400 HZ one having been removed.  I also have one of the TN-2 tuning units, which I once combined with the 30 MHZ IF of a Northrop Ventura UAV command receiver to produce the world's worst FM receiver.  I later used the 26 MHZ IF of an ARR-52 to produce the world's second worst FM receiver.  I also removed the acorn tube and replaced it with an FET to make a VHF signal generator of limited stability and doubtful utility. 

Wayne
WB5WSV