In 1960 and 1962 to 1969, most stickers had a 6-digit serial number, but stickers for tractor and trailer plates started with a "T" followed by 6 digits.
It looks like all stickers for 1970 started with "T", then starting in 1971, the "T" was dropped and all stickers only had the 6 digit serial number.
There were no stickers dated 1972.
Stickers switched from date-of-validity to date-of-expiration and new stickers reading MAR 73 were issued in 1972 to expire at the end of March 1973.
Non-passenger stickers initially expired in March of every year, but other months were added over time. A variety of fonts were used from this point forward.
The serial number was dropped during 1984.
All the sticker pictures above were enhanced from the originals to show detail - but follow exactly the original styles, fonts, and relative sizing.
Several years had multiple fonts (probably due to multiple print runs) and all the known variations/styles are shown.
From 2012 to 2014 only MAR stickers were issued - there were for 4-year trailer registrations and trailers always got March expirations.
From 1960 to approximately 1970, flat aluminum tabs were issued to be used on newly-issued glass-bead reflectorized trailer plates.
Evidently, stickers did not adhere to the glass beads too well, so tabs were used to hold the sticker.
Sticker on aluminum tab
Here is a die used to print APR 04 non-passenger stickers.