[Norbie]

To be more specific:
M = engine series
A = chassis series (RWD Celica/Carina/Supra)
6 = chassis generation (ie 6th generation of the A chassis)
7 = model variation

To confuse matters, in some cases the engine series may be two letters, and the chassis generation may be two numbers. For example, the current Celica is designated ZZT230:
ZZ = engine series
T = chassis series (FWD Celica/Carina)
23 = chassis generation
0 = model variation

Hope that makes sense.

 

[Norbie]

Just variations in trim/equipment levels.

 

[Norbie]

I might add that the MA71 did exist in Japan; a friend of mine purchased a JDM front cut which was an MA71. The MA71 certainly isn't a "US reference" because some Australian-delivered models were also MA71's. To add even more confusion, I have seen MA70's with factory-fitted 7M-GTE's.