Just adding another data point. The originals from my car were stamped on the inside and the outside...
D/S Outer: 8 19 D2 = August 19, 1966 - Dearborn, MI / 2nd Shift
D/S Inner: 8 26 2D = August 26, 1966 - 2nd Shift / Dearborn, MI
P/S Outer: 7 20 D3 = July 20, 1966 - Dearborn, MI / 3rd Shift
P/S Inner: 8 26 2D = August 26, 1966 - 2nd Shift / Dearborn, MI