Hi Hans,
I've researched this wheel a bit as I picked one up earlier this year. I actually emailed you about it if you recall. There are a few folks that have this wheel in their car, I can think of three off the top of my head. One of those cars was an Alpina B2S. My understanding is that the wheel that you have pictured is in fact the early CSL 380mm wheel. I've read on the forum that the Petri came into play in 1972, which means that only the very early CSL's got the prototipo. Our registry site has 8 1971 CSL's registered and 60 1972's.
The tricky part for me is the content that I've read and you reiterated is that the stacked momo logo went through 1974. None of the 380mm Alpina wheels that I've seen have a stacked logo, and that doesn't align with the early CSL production range. What is consistent with your wheel and other 380mm Alpina wheels that I've seen is the rear facing Momo logo, Made in Italy on the back, Alpina logo placement, and missing date stamp (which put's the wheel around the mid 70's like you said). What I haven't seen in other examples is the Prototipo logo on the wheel face. All of the other 380mm Alpina wheels that I've seen don't have the logo. It's possible that the paint wore off on the other wheels, but I've seen some pretty clean examples online.
Incidentally, the other thing that I'm trying to clear up about this wheel is if the alpine logo was engraved before it was anodized or after. After makes sense since Alpina got the wheel from Momo. My logo is black but I suspect that it's from an earlier restoration.
