If you've forgotten I found an '85 M5 for sale on Classifieds2000.com and emailed the guy out of curiosity. At first it sounded fishy but sure enough, it was a Euro M5 import. I came across it again and now I know another piece of the puzzle (like anybody cares, but i still think it's cool). Turns out it was imported by Johnny Miller (a golf pro apparently) in 85 and has since been religiously maintained.
In case anyone's buying there's this one and another on sale currently on ebay.com.