How to know my Apple Watch model A1553 series?

I have an 7000 series 38mm Apple sport watch which I purchase when they first came out. I can’t remember the series for Model #M1553. I need to know if this is a series 2 or 3. I reset the watch and didn’t want to sync my phone back to get all the information again. I’m trying to sell it

[Re-Titled by Moderator]