It's an old I frame, like this one but in much rougher shape:
Her images to me weren't very good, but it was enough for me to ID it, and she affirmed that the above is the same model. So, #55870, combined with that, enough info to give me a guesstimate as to what year it was made? Otherwise, I just told her sometime between the wars.
Thanks again - to you, to laytonj1, and to everyone else who has helped over the years.