Yes I think the shutter is single curtian, certainly looks like it when looking at it fire with the back open. And yes, the shutter speed dial rotates really fast when shutter triggered, get your fingers in the way and you slow the shutter.
First roll hanging to dry, and it looks good. GP3 cut down from 120. Speeds tested 1/25s, 1/50s, 1/75s and 1/100s. Before scanning it would seem that these are pretty much spot on. Quite chuffed.