[jocko]

One nuance about the early 73-75 3/4-1 ton PO3 caps is that there were concave (innie) and convex (outie) varieties of the yellow bow tie center. 67-72 PO3s for 3/4-1 ton were all convex outies. Convex 73-75 PO3s seem to be fairly uncommon, most that I’ve seen were concave. (and note all 1/2 ton PO3 caps are concave innies).