Your serial number i.e FCC ID is located on the bottom of your FITBIT watch box. On watch, go to settings & scroll down to Regulatory Info. tap on it. FCC ID will be there & if it is your watch it will match the FCC ID from the bottom of the box.
Abhi toh sense 2 bhi launch ho Gaya he, www.amazon.in/dp/B0BF4S2CCT Sense and versa meh Kuch features ka difference he jisme sense meh jyada features available he.