I have visited the Lisle Manufacturing plant that made the original plugs. I tried to see if they could make them again with the same original lettering. No dice.
I believe the LISLE 3 plug was in use prior to the M22 being introduced (so it is prior to 1965).
There are at least three minor variations of the LISLE MAGNETIC 2 plug. The 1969 model year type plugs were also used in 1968 M22s in Camaros.
From what I can tell, the P and LISLE plugs are 1970 and later. Possibly some in very late 1969 but not sure on that. Typically used when there was both a fill and drain plug.
The W plug with underline is a fill plug, the normal plug for M20 and M21 transmissions 1969 and earlier.