The '94 through '96 125 had TM engines, I know. I didn't see any more 125s until '01. Those had the GasGas engines.
The '94 and '95 EC250 had TM engines. Paul Edmondson (sp?) won the WEC on one.
I have the parts books for those bikes, if anyone needs parts numbers.
The pistons interchange between GasGas and TM. (I used to stock Vertex TM300 pistons for my customers, because I could get them from Tucker Rocky, as a less expensive source than the (then) OEM Wiseco.
I was sure glad when they got Wossner to make pistons for them in 2004. That made them available "aftermarket" both as Wossner and Athena (also Wossner, but with the coating, as Wossner named pistons come now.)