I can't find anything about it anywhere
A vintage MAC S-17 carbon scraper - and the only reason I know it's a carbon scraper is that a mechanic told me that's what it is, even though he'd never seen one like this before.
I'm going to use it as a wood scraper to use to work on the carvings and inletting I do on flintlock rifles, just have to adjust the angle of the scraping edge and put a burr on it.
https://archive.org/details/MacToolsCatalogueNo47/page/n15/mode/2up
Modify it, worth more as a tool you can use than a collector piece