You may see Japanese web sites remarking that the 1200 2-dr GL Sedan was known as "GTR". This is not a myth... because "G" is the code for GL trim, "R" is the code for 2-dr sedan and "T" is the code for 4-speed.
The Datsun 1200 GTR is even listed in the parts catalog, and debuted after the other 1972 models
Of course this nickname is also a play on the most famous Nissan Skyline C10 GTR -- which looks a lot like a larger version of the 1200 2-dr sedan (except for the headlights):
GX 1200 sedans were 4-dr only:
A 2-dr GX would have been a KTR if the factory had ever made a 2-dr GX.