Hirth & Krause, Dealers in…Leather and Findings. Shoe Store Supplies, etc. Grand Rapids, MI: 1890.( p. 46)
Kevin Driedger , who writes the interesting Library Preservation blog, posted a useful comment a couple of months ago, wondering if I was making an erroneous assumption about how a Turkish bone was used. I guessed it was used for marking. Lately while reading a old supply catalogue for the shoemakers I realized it that shoemakers have two distinct types of bones, termed scratch bones and slick bones. Now I’m convinced that the Turkish cobbler’s bone I wrote about is a scratch bone. Turkish shoemakers now make European style shoes, not Ottoman.
Judging from the catalog descriptions, it seems the scratch bones (similar to a scratch awl?) were used for marking, and slick bone was used for burnishing or smoothing. I wonder if the right angles on the left end were also used to scratch a line? This shape, seems to have served as the template for the most common shape that bookbinders use, with one flat and one rounded or pointed end.
Below is a slick bone that I purchased with some other shoemakers tools. It is thicker than most of the cow bone folders that are commercially available to now, and has a pleasing natural shape. The facets of the somewhat crude shape are highly burnished, suggesting it was used with a far amount of force or speed, the accumulation of glue residue and deep scratches give it a gorgeous patina from use.