[Arran]

The VT71 Motorola, and related models, are the closest television equivalent to an AA5 built in the late 1940s. I think Bob Andersen said that they sold for under $200 whereas an RCA 630TS and it's successors sold for about double that. My guess is that this 48-700 was somewhere in-between, like the electrostatic Admirals which also used a proper power transformer. One thing you could do is take an ohmmeter with you the next time you go and look at it and check the picture tube heater and the power transformer windings for continuity, you can check the B+ winding by measuring across the rectifier tube plate pins and across the power cord plug for the primary, etc.
Regards
Arran