In general, the pattern of lock pins tells one nothing much about the genetics of the gun. Virtually 100% of gun locks at this time (late C19th) were supplied complete but unfinished by the major lock makers in the Wolverhampton area: Chiltons, Brazier etc.
There are a few basic designs, mainly based around the type of interceptor sear used (if at all) and the pin patterns may look radically different from the outside but the mechanism plan inside are very similar.
What you are looking at are main spring peg (either bar or back action), Int. sear spring, Main sear spring, Int. sear axle, Main sear axle, Tumbler axle which gives 6 pins in fairly fixed positions. The balance are the bridle pins: 2, 3 or 4 and their positions can vary greatly with cost, quality and mutation over time
Absence of the int sear and its spring reduces pins by 2.
Also in locks that use the Robertson favoured 'Spear' int. sear there is often no external evidence of a pin as the int. sear was mounted on an internal boss and retained by a pin in a blind hole.
On some lower quality, cheaper locks, there is no main sear spring, the lower limb of a back action main spring performing this function.
And don't forget that some lock pin patterns are simply designed to confuse the unwary shotgun historian!
![[Linked Image from i.imgur.com]](https://i.imgur.com/qclHjMQ.jpg)
