Really a WWI (1914-1918) watch?
Vintage Military trench watch Tissot | eBay
"This watch i purchased from an antiques dealer. It is a military issue tissot from what i have been told. I cannot open the case back because i do not have the tool.
The watch runs sets and winds. I do not know how accurate it is. The bottom of the dial read swiss model. The dial is very clean and sais tissot windsor.
Trench watches were all made with similar swiss movements. Therefore it may not be stamped tissot. The reason i knoe is because i have another trench watch that does not have a brand name stamped on it. "