unfortunately everyone seems to think that there's no such thing as a 1968 Trident
The information you have been given is basically correct, in that the are are no actual '
1968 production year models'.
But... the *production year* of Triumphs and BSAs did not match *calendar* years.
Production of bikes for the new year season normally started around August of the preceding year in order to build up stocks of machines and to enable them to be shipped worldwide (mainly to the USA) for the new year season.
T150 production for 1969 actually started (somewhat slowly) around June 1968, at engine/ frame number *T150T 101*. These early machines have some slight technical differences, like the 1968 pattern front brake etc..
Later in 1968 the BSA-Triumph group added a two letter date code prefix to their numbers (see additional note below), the first letter showing the month, and second letter the *production year*.
http://www.triplesonline.com/bikes/dating.aspThe first production year letter used (for 1969) was *C* so for instance, a Trident with an AC number prefix would have been assembled around January 1969, however one with, say, an NC prefix would have actually been assembled around October 1968. But if your T150 is a very early 1968-built one, then it won't have that two letter prefix anyway. Practically all of the early production bikes went to the USA, as they were not generally available to buy, even on the UK market, until early 1969.
The engines were built, stamped, (the date code stamp was added at Meriden apparently) and then stockpiled until they were used on the production line, as Triumph Trident engines were actually made at the BSA plant at Small Heath and then delivered to the Triumph factory at Meriden.
The engines were then used on the Meriden production line in a random sequence, the frames being stamped on the line to match the actual engine number that had been fitted.
TriplesOnLine
http://www.triplesonline.com/ is a very good website for Trident and Rocket 3 owners to find out information, and it has an excellent forum, and I hope you will consider joining the group?
AdditionI believe there is some disagreement about the exact month that the Triumph factory actually started using the date code system on Tridents?