I love these!
A mechanical victorian charm, modelled as a roulette wheel under glass, with a little white ball. There is a lever at the bottom of the charm that you flick with your nail, and the wheel and ball spins around, the ball finally landing on red or black, with also a number.
The back of the game is set with a banded agate which you could get engraved; and the side has a gold rope twist detail.
 
weighs - 11.86g
measures - 25mm diameter, about 10mm deep
I havent had it tested but it looks like 15 carat
 
English circa 1870
 
condition - In good working order.
Needs a good polish. There is a nick in the glass on the inside which you can just make out on my pic (if you pretend it's a clock it's at about 10pm) but you can't really notice it and it is not a crack. The glass is a bit scratched.