Look at the left side of the engine just below the cylinder cooling fins...! There should be an engraved tag which says 196 cm3 if it is a TW 200....!
click to enlarge the pic
And i'm bit confused about your model analysis..! TW200 has disk break and all the new features as the new 2014 model from 2001 onwards..!
I have no idea about TW125 though..! It was never introduced to our markets..! (South East Asia)