English Market Gun Question

[VintageShooter]

I recently purchased an English market fowler, 12 ga. It is signed R. Hughes. R. Hughes was a Birmingham maker 1855 - 1858. I bought the gun because it had an unusually long barrel (48") and was in excellent condition. The lock is unusual. Instead of the standard three position (fired, safety, and full cock), it has four positions: fired, safety, and two cocked positions. I cannot tell any difference between the trigger pulls. Has anyone seen this before? Does anyone know why a lock would be designed like this?

Vintage Shooter

 

[Loyalist Dave]

Assuming this is a caplock....

My Scientific Wild Arsed Guess (SWAG) would be if for some reason the caps were known to sometimes take more force on impact depending on the cap making company, to cause the chemicals to combust. So, the shooter would test the caps, and find that caps from X maker needed the second cocked position to reliably shoot, it having more impact force that the first cocked position.

Any of you British folks know if me the Guessing Yank in this conversation is correct?

LD