Your Model 1849 Pocket Revolver appears
to be factory
engraved, and the ivory grips appear to be factory also.
You really should send off for a Colt Historical Archive Letter to determine if that's the case: http://www.coltsmfg.com/cmci/historical.asp
It's not cheap ($200), but well worthwhile in the case of a firearm such as yours, and documentation of factory engraving and grips would enhance the value of your revolver.
As to value.....there's no way we can give you even a ballpark estimate of a Colt of this potential value. It really has to be evaluated "hands-on and eyes-on" by a Colt expert.