You are looking at a Buick 7 blade clutch fan from a 65 Grand Sport with 400 / 325 HP Buick nail head engine and dealer installed air conditioning. Correct fan for 64 to 66 Skylark and GS with 300 or 400. It measures 18 inches with 1 7/8 inch pitch. There are no ID marks other than the ERX stampings. The blades are straight with no pitting.