This is a new 1956-1962 Chevy Passenger car and Corvette Non-Vented oil filler cap. This cap was used on cars with High Performance options like dual quad carbs and fuel injection. This cap is silver cadmium plated. We also carry the standard black painted vented oil cap in our store.
This application from the GM part catalog is:
1956-1961 Passenger Car 283 with 2x4 and F.I. (except 348)
1956-1962 Corvette 283 with solid lifters and High lift Cam.
Consult your restoration guide or forum experts to find out if this is the exact cap for for your restoration.
Original GM number was 1552719