Thom,
I think originally there were 10 sets of three covering the familiar road names of the postwar series.
Then, they began producing "archive collection" cars such as the solid shield Rutland and red lettered Western Pacific. Not sure sure how many of these there were.
Then, they did some "overstamped" cars with one road name stamped over the original. Again, not sure about the number of these.
I don't think there was a lot of interest from collectors after the original 30 or so, and some of the more famous archive cars.
Jim