1" tall (not including ring at top) and 5/8" wide. Closes securely. Made of two halves of what I think is river mussel shell // nacre // mother of pearl. The findings and frame are Pinchbeck-style imitation gold. It's French - the directions on the little glass-fronted compass are N/S/E/O(Ouest). The mercury-filled thermometer is intact, and the hand-lettering gives the temperature in Centigrade, with "GLACE" written at 0 degrees c (the freezing temp of water.) This could have been made in 1850 - 1900, hard to say. COOL!!!