I have been looking for a list of the different versions of the Simpledrive, and what the differences are between them. The best I could find was a post from 2 years ago in the B/S/T forum, but it only listed the I and II.
I have one that I got on ebay several months ago. It's marked with "Simpledrive", "5Ar1", and what looks like a serial number. The main things I'm interested to find out are: What is the difference between this and the v4500, and are there known issues with startup spikes on the 5Ar1? (I have read about some other versions having those kind of problems.)