Dates on lock plates are seldom seen. Not sure why, but the old gun makers and locksmiths never found it desirable to date their work, with some notable exceptions, (Oerter, and Schreit come to mind here). I have only two KY rifles, an Ohio gun, that is dated, (1850), and an NC rifle that has a date of April, 1819; (that is two out of 50 and I haven't seen more that on scores of other pieces owned by other people). You will tend to see far more signatures on pieces than dates, and nearly always on the barrel flat.
A date isn't an impossibility, but it is more likely that you will fine something like " & Co." or "Bros" or other indication. Please let us know what you do find as it will be an interesting item of information for all the rest of us.
You are fortunate to have a nice original local gun that has family history. Thank you for displaying it! Don't do too much to it; looks darn good as it stands.
Best-Dick