You need the II. The old version used a different type of mount (it screwed in, if I remember right, which the new one had a bayonet mount). The older one is for Autometer II. The new style is for the Flash Meter II, III, IV, V, and VI and the Autometer III, IIIf, IVF, and V.
I have a 10 degree II and an Autometer IIIF that I bought new when I was 15 yrs old. The 10 degree II works well and is really the only usable solution for reflected light metering with Minolta's incident meters, since the regular reflected light attachment is just a hole over the sensor with a very wide angle of view. I remember my 10 degree II was $100 new back then.