I am inclined to think its later - probably closer to 1790 despite its archaic look. I'm basing that impression on the lock which looks to me like a typical post-Revolutionary B'ham export product.
Also, I can't remember ever seeing the word "warranted" on a believable Revolutionary War lock although this became something of a "catch word" on everything in the post war period.
However, the waters here are pretty muddy. Beginning with CW Sawyer at the turn of the century, many post-Revolutionary guns have been attributed to earlier dates. Even if we've been able to sort our some specific instances of this, the collective notion of what a Revolutionary War period gun should look like is still influenced by authors who were working with far less data than we currently have. There isn't even much evidence that significant numbers of English-made locks were exported to the colonies before the war. It appears that it was far more common to export whole guns, that the market was dominated by the London trade (not B'ham) and that assembled American guns, as often as not, reused parts from older guns rather than being made from new imported parts.
