Except that Kodak stopped making Tri-X Pan sometime in the '90s and replaced it with New Coke 400TX which is NOT the real thing.
Tri-X was a traditional round grain film; it had a gritty-grainy, high contrast look that street and rock music photographers loved. It also could be push-processed several stops, so it could get printable images however low the light. Whether its merits ever matched the legend is another matter - but a quick way to start a fight on any film users' chatroom is to express doubts about Tri-X.
In the 1980s a whole raft of tabular grain films appeared. The tabular grains use less silver, so the films were cheaper to make but could be sold at higher prices because they were "technologically more advanced" (where have I heard that recently?). Kodak's 400 speed tabular grain film was T-max, which is still sold. Like the other tabular grain films, however, T-Max performed less well than Tri-X (as all the other tabular grain films performed less well than their round grain equivalents) and T-max sales collapsed. Kodak still wanted to reduce its silver use, so - according to Steve Anchell - they then reformulated
all their films using dye linkage because that also allows less silver to be used. So Tri-X became TX, but TX still has rounded grains and high contrast.