I had this fall in my lap today for the cost of FREE. It's a Gibson GA-20 in seriously beat up condition but it's mostly original. A couple of Caps look like they may have been replaced and there is some evidence of other work like some shiny solder joints here and their. It looks like it's a 1951 to 1954 model. The tube numbers match for the model amp and the speaker is original. It's exactly as it is described here: http://valvealley.com/the-amps/amp-page-2/ except that the output transformer is attached to the speaker frame. Looking at it's condition I don't think it's worth much unless someone wanted it as a project. And I need another 'guitar' project like I need more poison ivy rashes and beside wiring guitars is the extent of my electronic skills. I've read everything I can on it and know that Ry Cooder is the musician most associated with this amp and that the Gibsons were cheaply made compared to Fenders of the same era. I'm not really sure what I want to do with it at this point. I mean I know my options, take it to a tech, see what a vintage amp 'shop' would give me for it. Sell it to someone who likes this kind of project. . . It is kind of cool just having an amp this old.