There was a large Goulcher/Golcher family in the B'ham gun trade... all described as being "Gun Lock Makers." I'd be astonished if it wasn't the same family. They appear on the American market just as the Ketland's are disappearing - dying off would be more appropriate. My own feeling is that they saw a market reopening and jumped at it. We know at least one, and probably more emigrated. Whether they actually made locks here or imported them and said they made them here is a question. Were it not that they actually claimed to be making them here, I'd just presume they were all English made. I suspect that they may have started importing lock and gone on to importing parts and finishing them here - provided the members of the family that did emigrate had the proper skills. Its very difficult to say from this distance in time. They would have said them made them here whether they did or not and this would have been a perfectly acceptable business practice for the time.
John Dent Goodman relates a story of being underbid on a lock order while in Philadelphia around 1853/54... he went to see what American could possibly underprice him and found a member of a family he knew. In fact, he claimed he would have ordered the locks from them had he gotten the order. Unfortunately he does not mention the name but the story he relates was that this gentleman had emigrated only to discover he could not find work ... he was a lock finisher. He was importing rough parts and finishing them himself in order to survive. I've often wondered if it was one of the Golchers.
There is also some issue with materials. Gun locks used a good bit of steel that wasn't made in the US. A major bone of contention with the National Armories was that all the steel for locks, bayonets and ramrods was imported. The politicians were constantly demanding that the armories "buy American" and the Ordnance Department was just as consistently refusing to do so because the quality of American steel was so low that a huge percentage of parts were rejected. A civilian maker would have had to import his materials too. Between the cost of materials and the lack of skilled workmen it was effectively impossible to manufacture locks in the US. Remember, even Colt, had to import his steel as did Remington for his steel barrels. The primary material, crucible steel - or "cast steel" was never successfully made here.