You must have a late 1970s Campy Pista crank, after the point at which Campy changed the BCD from 151mm to 144mm. The BCD on the road Strada cranks was 144mm at that time, so that it was hard to tell them apart, except for the shoulder on the inside of the spider for the inner chainring on the Strada. I have a Strada double on my vintage Ron Cooper road bike from the same era.
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