T="thread"
F="filo" (Italian for thread)
I think it's similar to how Campagnolo has variously marked their parts "Brev. Camp." and "Pat. Camp." where Brev. is an abbreviation of brevetto (Italian for patent) and Pat. was an abbreviation for patent.
Last edited by JohnDThompson; 07-27-15 at 11:17 AM.