Francis Sell probably had a Cascade Snap Shooter receiver sight on his rifle.
Sell had a hand in the development of the Snap Shooter and wrote of the sight in several articles including the Handloader September 1982 article on the .25-35 Tomcat.

Sell also had the sight on his Husqvarna chambered for the .30 Short Ackley Magnum. Sell wrote about the rifle and cartridge in the 1961 Gun Digest article: The 10% Rifle.
Francis Sell was an interesting and well rounded man. He was a genuine Gun Crank and knowledgeable about firearms and cartridges.

I formed a lot of my opinions about small game hunting cartridges and rifles from Sell and Vernon Megee. In the 1960’s I had my nose buried in the Arms and The Man and the early American Rifleman magazines. Sell had articles in all of the magazines and you had to hunt for them. This was the days of iron sights and low powered scopes. Pre Red Mist.
Here is a picture of Sell in the July 1958 issue of Guns with his Husqvarna. I was disappointed it was not a Model 64 or 71.

Cascade Snap Shooter on Marlin
[Linked Image from i.imgur.com]
Cascade Snap Shooter on
[Linked Image from i.imgur.com]
Franscis Sell My Favorite Gun
[Linked Image from i.imgur.com]

Last edited by william_iorg; 03/26/23. Reason: added picture

Slim