Dear Sir - As Squire Robin notes, your lockplate shows the cypher of the East India Company. The standing lion holding a crown was adopted in 1810.
Previous to that, the lock markings on the East India Muskets were the 4 quartered heart with the letters "V" (United), "E" (East), "I" (India), "C" (Company) with a cross or the figure "4" at the top (the cross was changed because of Moslem objections). The contractor's name was engraved in the center and the date above the heart.
From the mixture of markings on your piece, and the rather odd selection of marks on the lock itself, I am of the opinion that you have a Khyber Pass special, made to please the many tourists in that part of the world for the last 200 years. In comparing the fit and finish of your lock with that of a Pattern 53 from 1861, yours appears to have been made by somebody who has certainly seen one, but not clearly.
Our American brothers-in-arms are bringing these 'antiques' back to the US by the container load, in the mistaken belief that they are valuable antiques. In truth, 99% of them are made up from bits left over from other bits left over from making other bits. The poor finish of the curved cut-out at the breech end, where the pen-knife used to cut the curve can be clearly discerned, are typical of the genre, as is the habit of cutting bits off, like lugs, or putting bits on, like sights. A look at a genuine P53 or similar weapon of the same era will show a clean, machined finish to the wood in this location - because it WAS a machined finish. The appearance and colour of the wood is also a mite suspect...but then I'm not an expert. All I know is that my two old Sniders, fence post drivers both, rather than tack drivers, have much closer-grained stuff of much darker colouration - less like a modern wood dye.
Interesting for what it is.
Enjoy.
tac :grey: