I've got a project gun that is missing some screws. It's an early 1900's German made double barrel shotgun. The floor plate screws from the action are missing. It was someones project and the screws were lost before I acquired the gun.
Quality of the gun makes it worth my time to put the TLC and effort into repairing it.
It's easy enough to figure out a external thread when you have the screw, but when you only have a tapped hole, how do you determine the thread?
Being pre-WWI German, I'm betting it's metric, but is also potentially a custom thread from before the days of standardized fasteners.
I can get an idea on minor diameter by using drill shanks, would assume it's a 60 degree thread form, but how can you tell the pitch?