If you want to find a close fitting replacement, you need to provide accurate dimensions of: length of mortise from back to front edge at longest spot; height of mortise at about where lock bolt is located, height of nose area of mortise at about where the nose area starts. Also provide distance between center of tail of lock to the center of the lock bolt hole...and the height up the center of the lock bolt hole is from the bottom of the lock mortise. Pictures of a tape measure held next to the mortise are of little value since they are too fuzzy to read accurately....you need to take the physical measurements accurately yourself and post the numbers here...to the closest 32nd of an inch hopefully.
You will not find a perfect fit, so you want to look for the closest fitting lock plate that causes the least amount of removal of original stock wood to inset it. Often you can find a lock that fits pretty well into the mortise in the rear portion, but is slightly too long in the front nose section. Your rifle has ample extra wood there to allow a slightly longer plate to be set in snuggly with only minimal removal of new wood. If you find a plate the fits reasonably well, just slightly loose, it's not a bad one to use, since a lot of old lock plates that have been in and out of guns over the years become slightly loose in the mortise.
A big problem will be finding a plate with the proper size and location of the cut-out for the round side lug where the nipple fits. If you find a usable lock plate, then a good idea is to have a good metal worker "move" the rounded cut-out for the side lug by welding in metal where needed, and removing metal where needed, until the lock fits around your specific lug reasonably well. Lugs vary a lot in size and their cut-outs in location, so a little metal work in this area is almost unavoidable....if you want to find and use an original lock. The metal worker may also have to relocate the lock bolt hole slightly...by welding up the old hole and drilling a new one in correct location and correct size.
Another approach is to purchase a modern percussion lock (Dixie Gun Works catalog) and have a metal worker file/grind/trim its edges until it fits the mortise correctly, then make the side lug cut-out to exactly fit your rifle. Problem with using a new lock is that it usually has no name on it, often no border engraving, and needs to be colored and antiqued down to approximately match the finish of an old lock that would be on the gun. That requires a competent metal worker who can engrave, and who has worked on restoring old locks in the past.
Perhaps if you provide good dimensions of the lock mortise on this site, some viewer will have a spare that is close to what you need, and may be willing to sell it to you.
Shelby Gallien
