A couple of Japanese web sites say the 1200 2-dr GL Sedan was known as "GTR". Perhaps this is a myth... but maybe not ... because "G" is the code for GL trim, "R" is the code for 2-dr sedan and "T" is the code for 4-speed.
Of course this nickname is a play on the most famous Nissan Skyline C10 GTR -- which looks a lot like a larger version of the 1200 2-dr sedan:
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.