It looks like a restock of a Grice or Wilson of the sort Shumway presented in the old Buckskin Report series of articles. I have the articles, PM me if interested. Should have "LONDON" engraved in script on the barrel.
I think the originals all used a catch that was driven straight down into the patchbox cavity and caught a square hole in the lid. They were stocked in English walnut.
I'd say the barrel, sideplate, buttplate, guard and patchbox are from an earlier gun (a Grice or Wilson trade rifle, now restocked here in maple)- the lock, if from the same gun, should have Wilson or Grice engraved on it.