I believe the only watches ever marked for 8 positions adjustment were by Gruen from before or near 1920
for a few years. Seen in 17j, 19j and mostly in 21j but not frequently even in their best Extra Precision versions. I have 1922 17j and 1925 21j. Marked always with temperatures, not singular temperature. So I think actually 6 position with a couple repeated after temperature testing. RR watch experts generally disagree this was valid marking, but although Fred Gruen did flamboyant agressive advertising at the time, except for the 50th decorated special, movements were conservatively jeweled and designed for real quality. Their most expensive production model Ultra Verithin at the time, was very plain appearing 17j movement. Notice how the 2 later ones are emphatically marked eight to help validate the marking. Also the odd feature I also think unique to Gruen adjuster screw near 8 marking is missing from later movements. It is for selecting winding or setting when removed from case or without stem. Original with the better grade Verithins, but indicated here obsoleted about 1925. Images here 4 different movements.
2 cheap ones mine.