Actually what I am most interested in is the casting date of the toploader case as that gives us an exact period of when it was made as related to the drain plugs or no drain plugs. The D119 that is cast into the case translates into April 11 1969.
As another example, I have a case here cast with an A120 which make it a Jan 12 1970 date. Its stamped with the VIN and matches the car which was built middle of June 1970. Big gap between cast date and assembly of the car but as I am expecting no drain plug.