to differentiate between type "M" and "S," here are some overall cues:

-type-M has better brakes, 4 pot on the front and 2 pot on the rear with nissan printed on them, type-M also has upgraded interior, along with a motorized front spoiler.

-GTS type-S has a motorized spoiler as well; its an option on all models, so it's ruled out as an identifier.

-there is no gtst "type s."

-a type "s" exists as an r32 GTS - with hicas and the sports steering wheel in it.

-the type-M is what all gtst coupes are and some sedans; non-type-M gtst sedans have 16" alloys similar to the GTS, but are 5-stud.

-there's also a gts25 "type S."

-the sway bars on the non-type-M's are smaller.

-the proper GTS-t non-type-M (not a type S, just a type nothing) is avaliable only in 4door.

-the bone-stock GTS-t, non-type, has still got 5-stud wheels, comes with 5-stud versions of the GTS 15" wheels, the ones also seen on cefiros; they have GTS brakes, and the interior has different trim, no climate control and A/C was an option. they also have a different steering wheel instead of the nice leather one found in the coupes and GTR's.

-standard stock GTS-t, non-types, are lighter than type-M. so in standard form, they are agile, and can pull around 14.6 down the 1/4 stock, compared to 14.9 for a typeM.