This is a FORD 3 GROOVE CRANK PULLEY FOR A 289 CUBIC INCH ENGINE FOR 1965 1966 THIS FITS FORD MUSTANG and FALCON.
This pulley is unique to the Mustang and Falcon, with a smaller outer (Air conditioning AC A/C ) groove. Other Fords and Mercury cars had a similar pulley but with a larger outer groove.
It has been chemically stripped and zinc plated to deter rust and is ready for paint.