The story is that The Old Man got this from a friend at work—the guy was going to do the cabinet and my dad would work on the electronics. The guy ended up giving it all to my dad, who played around with it but said he never got it to work right. This was in the pre-internet 1980s and it was much more difficult to identify these things. He had a schematic for a different model, so that may have been the problem.
The cabinet says American Bosch, but if you want to look it up in Rider's Peretual Troubleshooter's Guides, it's listed under United American Bosch—that's useful to know if you're trying to find this thing. United American Bosch was the US-based entity for the German Bosch company (the one that made auto parts and is still in business). American Bosch made radios in the late 20s through the 1930s, but left the consumer market during World War II. They're now part of United Technologies.
Thanks to Google image searches and other people who put their radio collections on the internet, I found out this is a Model 36, circa around 1932. It's a six tube superhet. The Rider's literature uses the old 3-digit designations, so I'll do that here; if you're were going to order replacements, you'd want to go by the last two digits only.
551 (two): 1st detector and IF (equivalent to a 35)
227: Local oscillator
224A: 2nd detector
247: Audio out
As I mentioned above, the 51 and 35 are the same tube. I can't even find a listing for the 51 in RCA's literature.
This unit has a couple of interesting things that are new to me:
- the heater supply winding on the transformer is center tapped to ground
- the IF is 175 kHz, not 455 or thereabouts
Current status: on the shelf; needs cabinet refinishing; needs electrical/mechanical evaluation.