Angel,
The British have a 3" 10 gauge chambering.
The short ten had two chamber lengths:
1. 2&5/8" for brass shell cases in the very early Parkers.
2. 2&7/8" for paper shell cases in other Parkers.
As Charlie stated, there were relatively few 3&1/2" 10 gauge magnum Parkers. I think that Destry and Bill Murphy own all of them!
The value on your short 10 Parker will depend on condition and rarety. If you post some photos I think you will receive a range of potential value in a hurry! Please include a description and the gun's choke constrictions and weight.
Mark