This has been an interesting object to research. The shield & decoration on the back is a regular factory design. The serial number will give you the date.
I don't know how many examples have failed me up for sale. Prices are all over the place.
Google " Cylindre Huit Rubis" & sort out the similar auction details for your watch.
For example read more here.
Link
Antique Solid Silver Key Wind Pocket Watch - Cylindre Huit RubisCompletely serviced and now in orginal condition.Movement and case were cleaned accurately and the movement was oiled additionally.The case is in very good condition,The case covers open and close smoothly, the watch runs well and keep
sallysales.patternbyetsy.com
Ok, that is a Swiss Lepine Calibre Type V movement with a cylinder escapement and claiming to have 8 ruby jewels (in four pairs) for the train wheel pinions. (A lever escapement watch with 15 jewels - 8 train wheel jewels, plus four for the hole jewels and endstones on the balance staff, and three for the lever escapement (a roller jewel, plus jeweled entrance and exit pallets on the lever) - was considered "full jewelled" at the time, and ruby jewels were the most desirable kind of jewels, other than occasional diamond endstones on the balance cocks of some higher grade watches. A cylinder escapement needed fewer jewels for the escapement, if any.)
The Lepine Calibre Type V, a term which refers to the plate and bridge configuration of the movement, was produced in the many hundreds of thousands, perhaps even the millions, by many different Swiss makers, and had a production period that began somewhat before the Civil War and extended a bit beyond it. So that is a good sign. It was the most common Swiss export watch variety during the American Civil War. The "escapement" of a watch is the oscillator which regularly stops and releases the wheel train so that the watch hands can advance in a controlled manner. Cylinder escapements were an older style of escapement than the detached lever. They were perhaps a bit cheaper to make than a decent lever, but also mostly less accurate timekeepers.
The Swiss movement discussed here has a simple steel, or perhaps even a brass balance wheel without temperature compensation, which is similarly lower grade, as is the absence of a seconds hand, and the regulator is set way over to one end, past the end of its normal range, indicating that the watch is not keeping adequate time, despite the seller's claim to the contrary. The silver case and the movement have matching serial numbers, which is a good thing, and also not all that common for Swiss export watches of the CW period. The case seems on the light side, which is typical for Swiss export cases, but the condition seems good, and I've seen far worse.