I do not think that these are pre CPSC. They are I believe post CPSC gran sport. I guess the reason they are on so many bikes from the 70s is that front derailleurs were quite prone to breakage - overtightening of the clamp and misadjustment causing them to hit the crank. After 1978 the choice was simple - lipped with holes (super and nouvo record) and lipped without holes (nouvo gran sport). As the gran sport looks more the part many go for this. It is surprising how many "nouvo/super record front derailleurs" appear on Ebay that are in fact gran sport
Peter Geldard Surrey U.K
Cold but dry