What is it used for?

Decades ago I worked in an old power plant where the newest unit was built in 1952. All of the coal handling equipment had poured babbitt greased pillow block bearings for any shafting. When one failed, we'd take a rosebud and remove all the old babbitt. We had fixtures for the bearing blocks and would pour new babbitt into them. The it was Prussian blue and scraper time. Blue the bearing, check the pattern with a mandrel, and scrape the high spots in the babbitt with a bearing scraper until you got a good contact pattern. Then use a bearing groove gouge to make a grease relief and you are good to go.