Looks like one that sold on feebay a while back. They had it advertised as a drive wheel for a clockmakers' throw. I suppose It could be used to power any sort of small mill, turns, lathe, &c.
A topping engine, or rounding-up tool, is used when the teeth of a wheel need to be finished, after stretching or gashing. It uses what amount to rotery files, and has no indexing provisions save for the plates that partner with the cutters. Usually the work is bound between centres.
A more precise (and simple) way to top teeth is in a depthing frame with a steel runner and a fraise, or set of cone fraises, but they are less understood, and by and large less common.
It looks less like a common ingold topping cutter and more an elongated bevel pinion. It is swung in the depthing frame, and the wheel is adjusted side-to-side to run against whatever portion of it most nearly suits the profile of the tooth.
I haven't internet at home to snap a picture of them right away, but will put them on a disc and do it next time I am here at a relitive's.
Hey Miguel, I came across this lathe on the Internet. I thought you might find it interesting. The hand wheel is like the one you have although the mount is somewhat different. The lathe is probably English while yours is probably French or Swiss. However, I think the placement of the hand wheel is very similar.
You can see how it is attached to the body of the lathe. The crank is probbaly turned with the left hand as the tool rest is to the right of it.
Sorry, I cannot post the actual webpage since it's an ongoing auction.