I posted about this a couple years ago on a Marlin collector's site. It's a prototype completely functional receiver for a single shot based on Marlin 22 caliber pump action repeaters. About the only mention of these is in Brophy's book on Marlins where he says there is no indication that they ever tried to put them into production. It was during the Marlin-Rockwell years.
(You need to Login or Register to view media files and links)

(You need to Login or Register to view media files and links)

(You need to Login or Register to view media files and links)

The cost had to be high compared to most other single shots at the time. Looking at the details, they tried to cut production cost by making the top & bottom tangs the exact same straight contour to simplify machining and eliminated the machined step in the top of the receiver found on all the other pumps. These parts are not modifications of parts intended for a repeater. Even the locking arm is specific for a single shot since it's not milled for the parts needed to work a lifter.

There are more pictures and information here - (You need to Login or Register to view media files and links)

The only picture of one that is not just a modification of another model of receiver that I've ever found is the one pictured in Brophy's book on Marlins.
(You need to Login or Register to view media files and links)

The patent was applied for Dec 3,1921 but not issued until 1926.
(You need to Login or Register to view media files and links) 

Din't Winchester have an autoloader that fired a single shot?  You had to load the one round by hand, but then it fired and ejected automatically, staying open for the next manually inserted round.  I think it was for the children of worried parents who wanted an autoloader but the parents thought the kid would go nuts with all that fire power.  So a compromise was effected.

I've seen one or two examples at Gun Shows, but I get the impression that it sold like Nuclear Reactors.

Maybe this one-shot pump action was thought up for the same reason.  Looks pretty clumsy to load, though.

Nifty specimen you have, Gene. Thanks for the tale.

Gun companies of 100+ years ago were grabbing at straws every bit as much as they do today. Reading old Arms and the Man magazines and early American Rifleman's shows a lot of gimcrack ideas that never "made it into print", and therein lies a lot of stories to be told around the campfire today.

Let's screw a heavy RKS barrel onto that Marlin slide/single shot and see what it'll do off the bench on the 100yd. ASSRA smallbore target!

Gus Swebelius was another firearms genius, and a name most don't recognize today. He left Marlin in the late 1920's to start his own firearms company; High Standard Arms.
While at Marlin Gus also patented the interrupter that allowed machineguns to be mounted behind the propeller on planes and not shoot the propeller off. A major advancement in air to air combat.

Also curious.  After this single shot pump numbered
model 36, 
Marlin came out with the Model1936 lever action rifle as they discontinued the 1893, still with square bolt.
then shortened the model number into the Model 36, repeating the model 
number of the 22 single shot pump.
Then, later the Model 36 square bolt was discontinued
in favor of the  336, still kind of hanging on partially to
the number  36.....  curious....
beltfed/arnie