Actually, if James Goulcher's 10 year old daughter was born in England, and his 8 year old son was born in the US... and its the 1850 census, he emigrated sometime around 1840-41, corresponding to his renting the shop mentioned above. This suggests that any Goulcher locks sold here earlier were not sold by him. It rather looks as if actual manufacturing started in the middle to late 1840s, which makes a good deal of sense. By then the Ketlands, who had completely dominated the market, were long gone... the last Ketland firm, W. Ketland & Co., went out of business around 1831. The other firm, T. Ketland & Co., was bankrupt in 1821. This would have opened an opportunity for the Goulchers, who were neighbors of the Ketlands, and may already have had relatives in the US, thus being in an excellent position to step in.
All of this means that lock making for the civilian trade was essentially an English monoply, whether done in the Black Country or in Philadelphia, until the technological advances of the Civil War rocketed American manufacturing forward... but by then the emphasis was on breech loaders and other new designs. I think it unlikely that the British ever lost their dominance of the market as long as muzzleloaders were used.
Also, thus far I don't know that anyone has made a connection, other than the name, between the Revolutionary War era Goulcher and the later lock/gunmakers. It is an unusual name and it is certainly reasonable to suspect there was a family connection. However, the earliest date recorded by Bailey & Nie for a Goulcher provincial lock maker is 1827 so it is quite possible this is pure coincidence and that they are unrelated. The Goulchers/Golchers (both spellings were used) are really prominent in the British trade in the 2nd half of the 19th century, at exactly the same time they appear in America.
There are also Belgian-made locks with American names on them - there are some in the Liege Museum and they are mentioned in Claude Gaier's "Four Centuries of Liege Gunmaking" so there may even be Belgian-made "fake" Goulchers just as there were Belgian-made "fake" Ketland locks and guns. As soon as their name became well known, they became a target for this type of copying. I once had a brand new, unused early percussion lock - unfortunately I can't remember the name on it but I think it may have been Golcher. (Another thing I should have kept!)