Sachs made a straight 3-speed, and a 3-speed coaster brake version. Yours is obviously the former. I don't know how similar the internal planetary gears are with the straight model (I've only had experience with the coaster brake variety), but, if they are close:
1st = -27%
2nd = one to one
3rd = +36%
I've been told by an old bikesmith that the Sachs hubs had the lowest 1st gear of any 3-speed hub made. Kinda helps on the hills!