I bought NOS locks for the 1952 Chevy pickup in 1979~1980. A dealership in Arkansas had matched sets of locks in stock for many years and had answered a parts request from a dealership in Dallas when I requested these. I believe I paid $135 plus tax for both and it was well worth the cost. Nowhere was Cowles stamped on them but they were in boxes that were marked Genuine GM Parts...and I can't recall if the boxes looked like yours but maybe they did. They were exactly correct when compared to the originals and have held up very well.

~ Jon
1952 1/2 ton with 1959 235 | T5 with 3.07 rear end