Tissot used the 1340, 1341, and 1343 in different models. Sinn used the 1340, I think. I do not remember seeing a 1341 in a Sinn, but the primary difference between the 1340 and 1341 is the former contains 22 jewels and the latter 17. There are a few other small differences but nothing that can be seen on the outside. There is at least one Wakmann model that resembles the Tissot Navigator and uses the 134x.
My favorite Tissot with 1340:
Click to expand...