Hey are there some kind of markings on TB to let you know what size they are or if they are from an ATX or MTX??

 

there are a few differences between the 2...
if you look in the opening of them, the atx tb walls actually look kinda like a funnel being they taper down....the mtx tb has straight walls and is the same diameter all the way to the butterfly..

otherwise if you rotate the butterfly by moving the assembly that the cables hook to, you might be able to notice the mtx has a stiffer spring and the atx has a pretty light spring.....

otherwise i really dont know