The gunmaker is probably the name on the barrel. The Goulcher's were a family of lock filers (i.e. finishers) - originally from Wednesbury, near Birmingham in the UK. Some members of the family emigrated to the US and, supposedly, made locks here as well. I'm skeptical of that - I suspect they either imported them or, just as likely, imported parts and finished them here. Either way, they didn't make guns.
The rifle itself looks to be a fairly conventional heavy barrel "working" arms, suitable for hunting or target work (as target shooting was a popular sport) from the mid-19th century – perhaps 1840 to about 1860.
