Looks to be the 394...
Looking to get some spares for my 17C, what size do I need?
Don't take the screw out all the way...
tiny screw holds clip in, and it needs loosening only. If you unscrew it, the clip unloads and pings the tiny screw across the room into the cats mouth. Easier to not undo it all the way, battery comes out anyway!
A pair of sharp nose tweezers to pry one end loose is handy. I was lucky enough to lose, and find, the screw, twice!
The movement itself is magical compared to the pressed plastic tat that base ETA quartz movements are.