I think there were quite a few makers of unmarked gem pans, and this is a style that I see in almost every shop I go into. Often they have a stack or two like this, for $10-15 each. The casting quality varies wildly. I am in the northeast here, and people must have really liked these things, kinda like the corn cob pans are more popular in the south.
I do have one marked Barstow stove, RI and two made by Wood Bishop, in Maine. I don't bother with the unmarked ones, but if you want one to use, an unmarked one should work just fine, just try to find a bargain. If you are buying to resell, I would pass on these.
The one you have looks like a nice pan, Valerie, and in use would be the equal of a Griswold.