This is a Moser. I think the double chainring is a thing that was pioneered by a british chap(i have forgotten name) for standing starts in track pursuit. the setup allowed you to start in a lower gear(freewheel) and as the pedals went around a higher gear(fixed) was gradually screwing itself on to the other side of the hub and at some point became the final drive ratio. it involved a very careful setup to make sure the bigger gear didn't bite too early, or too late. i think that is hiw it worked and i beleive i did post this info and some pics previously on RB. can't find any info now, though. It was banned by the UCI.
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