Smith devised a tool for disassembly and reassembly of the mainspring. it is not necessary to take the lock apart to do this, it is also used to cock the hammer when lock is off the action and cock the gun with the barrels and forend off. See Brophy page 195. I have one of the tools if anyone needs demensions.

I learn something every day, and a lot of times it's that what I learned the day before was wrong