I can not read and unable to see the curvette writing/signatures; movement is nameless as many Swiss watches; yes, So. American can be easily referenced by the metal dial; is the watch running and have you weighed to watch in penny weights or grams?
Attractive enough and case appears to be solid gold. (There is nothing compared to holding an antique watch in ones hand to id. and value.)
This is a watch by Charles Robert Tissot of Le Chaux de Fonds. I assume (but I'm guessing!) that he was related to Charles Felicien Tissot who founded a watchmaking company in Le Locle in the mid-19th century. The cuvette (no "r") is clear to me, and in addition to the maker's name and location it says that the movement has a straight line lever escapement, visible pallets, Breguet-style hairspring, compensated balance wheel, and a double roller. Most of these are features of the balance wheel assembly. Normally I would expect a statement of the number of jewels in those pallets mentioned.
The movement of your watch is good quality, having a swan's-neck micrometer adjustment, and the balance I assume is cut (although I can't see the cut in your photos). I would estimate the date at early 20th century, although possibly late 19th.
The case looks well-engraved, although it is always difficult to judge this from photos. The representation of a horse being attacked by a hyena is pretty gruesome, especially given the idealistic horse's head on the reverse! The dial is a fairly common style of fancy Swiss dials.
Having said all of that, by far the largest part of the value lies in the 18 carat gold case. The inside of the outer case cover should show a Swiss assay mark - probably the profile head of Helvetia, or possibly a chevron - and it may have others. Please post a clear photo of this cover. Without an assay mark, the caratage is suspect. As Jon suggests, please weigh the whole watch and post that weight, and also post the external diameter of the watch excluding the pendant - we can then give you an estimated range of value estimates including the gold value.