The M61 was designed by 2 gents in the Winchester R&D Dept.
Harold Crocket (sp?) and Frank Burton

T.C. Johnson was head of the R&D and is sometimes given the credit for the Model 61 design and pat. But it was the above two that did the work and I believe their names are on the patents.

The 61 had to work around existing patented features of the FN Pump.22 already on the market (not often seen and I believe was not marketed commercially in the USA) and Remingtons Model 12.

The *Meriden Model 15 was pat by the two sons (John & ??) of Arthur Savage (Savage Arms Co).
Working for Meriden arms they also have their names on Meridens 12ga Pump shotgun sometimes called the Model 1912.

When Meriden went under never to return to business a the end of WW1/1918,,the pat and rights to mfg the *Meriden Mod1915 22 pump were bought by Oscar Mossberg.
He was just starting his company up in 1921/22 & started mfg the Mossberg Model M & K ( and L ?) .22 pump rifles which were built on that Meriden patent.

The Meriden pump 12ga shotgun I believe reappeared as the Savage model 1921 pump shotgun.
I have a Meriden 12ga pump and the Savage 1921 appears quite alike.
The Savage being designed and pat by Art.Savage' sons the other Meriden pat being sold off in auction may make some sense that the pump shotgun design could have ended up with Savage after WW1.
Often compared to the Win M12, it is more a hybrid of a Remington M10 bolt with a Win12 carrier & side ejection.