Powder Tester (Probably French or Belgian). These were used to measure the viability of black powder. The small amount of powder is placed in the barrel. A percussion cap is placed on the nipple. When firing the tester, a wheel with graduated numbers from 1 to 10 covers the muzzle, rotates to a number. A “10” would be an excellent reading for very strong powder. Very well made tester in excellent condition.