Copied from an original. Easy-to-read numbering. One side calibers up to 80, other side: shotgun bore up to 10. Also metric sizes. Handy carry-on key chain. Handy use in stores, firing line, gun shows, etc. Works best for muzzleloading guns. Made from German silver.
Punched for a lanyard, this nice brass gauge would make a shandy key chain accessory, or gentleman match shooter's pocket watch fob.