Big bronze and babbit plain bearing that are used in large machinery and engines. Same design as your cam and main bearing in your car, just bigger. I have a couple scraper like that from my Dad. He was a machinist and used to rebuild 6" and up bearing for punch press cranks. It is amazing the precision that can be attained with simple hand tools like this. I taught myself to scrape in order to rebuild lathes and mills. The straight-edge I scraped in checked out to be straight to 0.0002" over 12". That's two-tenths of a thousandth. A bit of beginners luck, but an experienced hand can whip that level of work out in very short order. A dying art.
