Yes it would be an 8” extended speaker. Yes it does have a transformer on the speaker as well which is why I do not know the value of it.
If I can find one I would sure put it to good use. This radio is similer to another radio I have for the same time period and it a 12-91x but can find no documentation on it. The only one close is data sheet 34 model 12-95,12-96 the output seem the same minus a few other tubes and regulator tube which I have not seen many of in Rogers radio. I belive the value is close to the 7R732 so it should work,if any one else can confirm this then I might know the value of the tranformer for the radio. I also belive this radio is a 1937 as the first number usally indicates this info. The other radio I am using is a 8R931 12/91X which I belive is a 1938 model.