I'm looking at buying a fairly rare radio from a fellow collector. Other than ebay, where do you find out what something is selling for? This particular one just doesn't show up on ebay.

radiomuseum.org seems to have some pricing, at least it's shown as a field in their database, but I haven't seen any numbers in that field. You might have to be a paying member to get that info, I don't know.

Suggestions?

There have been several antique radio price guides published over the years. I'm not sure how accurate/up-to-date they are though.

Another option is to tell us the model and hopefully get some responses from experienced collectors.

This is a Grebe Synchrophase, a later AC version called the AC-6 (1928). It's in very nice condition, and has the table/base with built-in speaker.

http://www.radiomuseum.org/r/grebe_synchrophase_ac6.html

You usually see the earlier MU-1 version with six dials, which seems to sell for $225 on average in good condition. I don't know if the scarcity of this model makes it any more valuable or not.

This Grebe page has a pic of one with the speaker table, about halfway down the page.

http://www.greberadio.com/

The MU-1 is one of the nicest battery sets around and has brought decent money for years.

Grebe's AC sets have not had the collector interest that their battery sets do. It's probably quite rare but the interest is what sets the price. Zenith blackdials are very common, yet also very popular.