I own an RA-103 in it's origional finish. It is definitely mahogany. The edges are painted a dark chocolate brown.
When I sand a cabinet after stripping, the roughest paper I use is 220 grit. 80 is way too agressive. That's why you burned through the veneer.
If that was an early RCA Victor cabinet, like that 721TCS I posted above, you would have burned right through it in about 5 passes.
Careful!
