One genuine GM NOS AC engine positive crankcase vent (PCV) valve. GM 8997683 / AC CV851C.  This old stock part is long discontinued. Shelf wear and staining to product packaging/box (see photos). Various Chevrolet, GMC, Oldsmobile, and Pontiac vehicle models 1980 thru 1990. 

Check photos for cosmetic concerns before you buy. Check your vintage GM parts catalog, or with your local GM dealer for vehicles with a VIN, for correct fitment before you buy.