The 'extra pin' I speak of is the screw (in double gun vernacular, pin = screw for most purposes) you see just behind the breech balls at the top of the side of the action, above the cocking indicator (it's been engraved with a simple starburst like the pins along the action bar).

The gold dot is the cocking indicator - not part of the sear.

The reason to illustrate this - inside and out - is to show that upper pin (which is visible externally) in relationship to the dog-leg shaped intercepting sears.
With this graphic image in mind, you can identify a boxlock with intercepting sears from a few yards away.
That could be valuable to you at gun shops or shows as you drift through the available stock.
The intercepting sear is not a commonly found feature - and adds greatly to the safety and monetary value of a gun or rifle.

Keep your eyes out for it.
Not all sellers know about this, and there are high-grade boxlock actions out there from (seemingly) obscure makers on-the-rack with lower marked prices than they might otherwise get.

Cheers
Tinker