I believe Briley makes "invisible" choke inserts. Finished (Soldered?) at the muzzle so that they can't be seen from outside the bore. They are not interchangeable without going to Briley or a gunsmith. Pretty good solution for a vintage gun that needs some choke, but I have trouble with this application. And 1/4 & 1/4? This is what I believe the auction house is describing - maybe not?? Between this, the rounded action, and single trigger, it is not attractive to me at well short of $150,000.