Registration numbers are unique through out the world.
Canada letters begin C-G??? or C-F??? as in C-FTCA
USA are N-##### XX as in N1234UA
United Kingdom uses G-????
France F-#####
etc.....
Most airlines around the world use a portion of the reggy for a fin (or tail) number as in D-GHDS they call it DS
Air Canada's C-FTCA is fin 658 and the 6xx series are B767 aircraft with fins 601-629 are 762 and 630 and up (except 671-672) are 763's