Hi Eric, I finally went to look at my Capehart Tv-radio-phono combo, and brought the owners manual home. It is a 504P. Also with the set, was a typewritten letter from the Capehart salesman to Mrs. Thompson (presumably the original owner), about the features available with this unit.

The letter indicated that more than one optional phonograph could be chosen, including one that plays both sides of a record. Also optional was the "Electronic Echo Chamber" for three dimensional sound as heard in an auditorium!

The item you mentioned behind the radio chassis is a loop antenna that is inside a cardboard enclosure. There is bold graphics on the cardboard promoting the antenna.

The small chassis you showed in a picture is almost certainly a phono preamp. It is intact on my unit, and is connected to the turntable that is in the cabinet.

I forgot to look at the channel indicator bezel, but when I return the manual to the tv, I'll look then.

I only scanned the pages in the manual that pertain to the phono, to save download time on this page. I would be happy to send you scans of the entire manual directly if you'd like. It would be 10 scans total.

Hope this helps you.
Mike