It's nothing very exciting, but has a good feel to it. A file holder specifically for small triangular files, as shown below, supplied with a modern file. Though the patent drawing is a bit different, the relevant patent seems to be 167,731, obtained on Sept 14, 1875, by H. Baumgartel (lovely name) of Sturgis, Michigan; see
https://docs.google.com/viewer?url=patentimages.storage.googleapis.com/pdfs/US167731.pdfOddly, I bought this thing in Scotts, Michigan, just down the road from Sturgis, MI -- though neither the buyer nor the seller come from there.
