I did a little reseach on the 931, the ad I have is 1941 and the model is the R 10 ,newer model, your 931 is a 1940 model and has, I believe, the older type antenna conection.
As far as value, if we all worried about that most of this stuff would end up in the garbage, to me that's where the modern stuff belongs, These old radio can be made to work now and another 70 years from now!
