w201 ac compressor (FYI)
 

Both of these compressors have been on my car. For the life of me I could not figure out why there were 2 different types of compressors for a w201. I have ordered 2 compressors in a span of 2 months and sent both back because when I got mine off, the opening ports did not match. I ended up ordering a brand new denso because I saw that it had the same opening as mine and the slogan on the box does say "first time fit" :D. Anyways, I took the top portion off the old one and put it on my denso. I had another old ac in the garage and I decided to do some cleaning and scrap a lot of the old parts I had, I got that old compressor and took the top off to keep as a spare and saw that the opening was not the same as the denso. So this whole time I could've actually used any of the compressors. So now I have both caps and I can use either or. Just thought I'd share this with you all in case anyone has an ac compressor fail, make sure you know which top part you have because even if you search for compressors specific to your model, you may get either or.

A review of this thread should be instructive as to another problem or two you might encounter when you get to the point of trying to install a replacement compressor; hose connection fit is not your only concern.
http://www.peachparts.com/shopforum/diesel-discussion/343287-possible-om603-96x-om602-c-compressor-upgrade-compatibility-discussion.html