You can tell by looking for (1) a pusher to advance the hours at the 4 o'clock position (in Gen2 but not Gen1), and (2) a red portion of the power reserve indicator (in Gen2 but not Gen1 -- and not visible in this photo).
in a number of areas they are different. The latest one has a different caliber. 72 hours power reserve. Pusher to set time disc, and then it is not limited. but both are almost equally beautiful