The cock on the lock of JTR's lock "appears" to be one from the Pattern 1800 & 1805 Infantry Rifle per Bailey's Small Arms book, mentioned in my previous post, page 75. That lock, per Bailey, was 1-1/16 x 5-3/8.
The crown on JTR'S lockplate is the "cartoonish" crown per Bailey's Small Arms book, shown on page 166.
From JTR'S photos, the fence of the pan is to the rear of the end of the barrel. Also it appears as though whoever adapted the lock to the rifle needed to drill and tap a new rear lock bolt hole as it wiped out the upper part of the crown on the plate.
Niall's observation about the lock on JTR'S rifle being an assembly of disassociated parts is very accurate. American Ingenuity at its best.