This is a very interesting shotgun. It was designed by Frederick L. Humeston who was an engineer at Winchester before moving to High Standard. (Humeston was the primary designer of the M1 Carbine.) The patent for his pump-action was assigned 1/2 to High Standard and 1/2 to Sears. The J. C. Higgins Model 20 sold by Sears predated all High Standard shotguns based on this design by several years, so it's really inaccurate to refer to the Model 20 as a "High Standard Model 200," as is often seen on the Internet. It's also been reported that the Model 20 was based on a Remington patent. This is clearly not the case.
If you compare the detailed drawings in the Humeston pump-action patent (No. 2476196) with those of C. C. Loomis at Remington for what would become the Model 31 as well as those for the Winchester Model 12, it's easy to see that Humeston was trying to integrate the best features of both of these guns in his design. It's no wonder many who have Model 20s (or later High Standard pumps based on the same patent) claim they have the slickest actions of any pump they've ever handled. With the Model 20, you've got the love-child of the Model 12 and Model 31.