History on Miller Trigger?

[Jessesky]

Hey guys,

I picked up this shotgun made by D.B. Crockart from Perth Scotland a while ago. I don’t know too much of the gun other than it was made in the early 1900s, is 12ga 2 3/4, and a 26” barrel. I suspect it was altered with the intent of sporting purposes like skeet or sporting clays.

It has a miller single selective trigger on it which I know is not stock or period to the time the gun was made. Anyone have info on these? Here is the pic from the auction.