The best quality DuMonts were made in the late 1940s and up to about 1951-1952. I believe an RA-502 would have been made around 1959, after DuMont's star had faded. Perhaps a decent TV, but far less interesting than an early DuMont, at least in my view.
Just my $0.02.
Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html