
if it is 10 years old, it could still be the older Zenith based movement caliber 4030. post 2000, rolex introduced new in house chrono caliber 4130. the technical differences between the two calibers to non technical driven people aka the vast majority of us is 48hrs zeith base vs 72hrs in house.
the main way to tell the difference between the two is simple looking at the dial. the second counters is at 9 oclock whilst the in house version has the second sub counter at 6 oclock(like the one above) the bracelet and clasp are also different, but not applicable in your case since you are considering on one on leather. there are other minor detail differences like brush surfaces at lugs versus polished etc....
I am not allowed to talk about absolute prices here, but the zenith based movements should be trading premium to in house.
lets see if the real Rolex experts will chime in.
best,
Horo