I still have a couple of rear mats from the old 66 coupe bought off the lot as a trade-in in 67.
They have C4ZA-6513054-F and P.P.I. 4250 8 with the FoMoCo logo on the back, while a nice used pair I bought on eBay listed as 68 to 70 have no part number on the back except for 1475 with the FoMoCo logo and Made in Canada and Fabrique au Canada.
RubberMaid did them all right?
If I had gone to the dealer in 69 to buy mats for a new 69 Mustang, which type would I have gotten?
I'm not saying it has to be one or the other of just these two examples I know of.