The one on the right is pretty common, and has a simpler spin mechanism. You just flip the lever on the right side of it. Cardboard dial. Lenny Schneir's catalog gave it a date c. 1920. It is cheaper and lighter than the one on the left. I'd value the one on the right as $50.

The one on the left is better, heavier, has the nicer mechanism (twist the top, push in to start and stop the dial spinning -- it spins forever practically). Enamelled dial. Lenny dates it c. 1890. In nice shape I'd value it as $75 to $150. It went for $250 in Lenny's 1994 auction.

Both show up on eBay a lot. eBay makes most things cheaper than they used to be -- supply exceeds demand.

Here are my roulette and gambling watches, from my web page:
http://www.antiquegamblingchips.com/RouletteWatches.htm