I have friends who are serious Remington collectors and have learned a few things from them and a little on this - The Routledge Bore is about 10~12" of smooth-bore from the muzzle end that is bored out to about 3/8" (guessing, could be more or less on both features), it created a larger more even pattern with the small amount of shot in a 22. The bore from the chamber out to that is 22 diameter smooth-bore.

Several companies marketed miniature skeet under different names. I don't know off hand which company had the one Lightfoot mentioned but Mossberg made rifles and throwers for miniature skeet, one thrower was made to attach to the barrel of the gun and had a lever so you could trip it with the gun shouldered, this didn't prove to popular because the torque produced by the thrower affected the aim of the gun to much. There was at least one gun made by Mossberg meant to be dual purpose, it had a smoothbore with two different screw on extensions, one was smoothbore and the other was rifled.

I have a couple examples of miniature clay targets called "SKEETER TARGET" the I think may have been marketed through Sears & Roebuck.

I know from friends with shotguns that guns could be sent to Simmons and they would install their ribs, so I would think the rib was almost certainly done by them, if factory, even it they had Simmons do it for them as a factory option, I don't think they would have Simmons mark it. I do not know if the Simmons rib helps or hurts the value, I will try and ask one of the Remington 22 guys next time I see one for an opinion.

The patent shows a two piece barrel but all I have seen are one piece & just counter bored.
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Last edited by GeneB; 04/08/18. Reason: reworded slightly & added picture

Gene