Van

That barrel was cut for a Mike Stevens removable base.  My first CPA some years ago Mike was making a good Soule sight & windage front sight, CPA furnished them.  Probably 10  years ago Mike passed away so no more from him.  Nice guy and excellent sights.   

Since I have bought sights from MVA and been real pleased.  They cut a special thread on one of there Hadley disk to fit my Mike Stevens Soule. I don't know if they will do special dovetails for front sights but expect they will if given the dims.  The Mike Stevens sights are pretty well known and MVA may be familiar with the cut.  I should also say removable is real convenient,  I only have one front sight and use it on 3 barrels.

Paul Shuttleworth ought to know what the dovetail cut is too and may have some information.

Boats

No worries,  I do think CPA switched over after Mike Stevens passed away.  Might want to make sure.  Paul keeps good records on his rifles and barrels bet his notes say exactly how it was cut.

Boats