U.S. Patent No. 431,207 (Patented July 1, 1890) by G.L. Gray "Drop Cabinet for Sewing Machines" ?
This must be it... Just for the heck of it, I am printing the patent out and will leave it with the future new owner of this cabinet. (I am not going to keep it, although the treadle is FABULOUS. I may consider another one with a more modern machine, post 1940's, in the future).
@ai6yr This is a great thread. I remember my grandma having one of these; the front edge of the treadle could come down on your toes if you weren't careful.
In the film "Fiddler on the Roof," a sewing machine played a part in Motel the tailor's "Miracle of Miracles."
@StumpyTheMutt @rationaldoge Interesting, similar design but different tensioning mechanism.