I was looking at my “Speedmaster” and I think I finally found out what the movement really is.
It is definitely not a Seagull movement, but a DG3836 from Man Power Technologies, Guangdong Province, China. This is around where the watch was made and has all the features of the movement. Automatic, with day at 9, date at 3 and 24 hour dial at 6. Looks like it is about a whopping $17 wholesale. It looks like it has 17 jewels, since there are only cap jewels on the balance wheel. If it was a 21 jewel, cap jewels would be evident on the escape and 3rd wheel.
It is 21,800 BPH, with only a 32 hour power reserve.
You can see from the wholesaler’s photos, this movement looks identical. I thought only my example does not have +/- or F/S on the regulator, but they seem to omit which direction will adjust the speed of the balance.by