Please consider donating to help offset our high running costs.
I’ve never seen a SM120 with that second hand. I’d say in all likelihood it’s a replacement
The only other second hand I know of is this one:
https://omegaforums.net/threads/a-seamaster-120-166-027-with-a-very-strange-second-hand.49425/
Although there are some theories about a orange second hand as well...
Looks like the second hand from a Seamaster 300.