I have one. Do a search on this forum to find a couple of older posts. I posted photos of what the original wet cell battery looks like.
These are quite heavy with the cast chassis internals. They also made a similar model with shortwave bands.
Yep, the battery had to be in place and charged. Mine will not work with the cord plugged in.
Some have suggested using a NiCd battery pack. I haven't experimented with my set yet as far as a new battery, even though I've had it 20+ years