It’s a 3-shot semi-automatic announced as a new development of “Izhevsk gunmakers” in 1959 (so it’s metaphorically if not technically the great-grand-daddy of MP153). It has alloy receiver with A-5-ish humpback profile and from the description it works on Browning’s long recoil principle. The prototype had replacable chokes with Cutts compensator.
What you think is tubular magazine is not – it’s just a hold for the barrel to travel over. Apparently, the two-shot mag is somehow housed in the receiver and/or the grip (sorta Cosmy-style).
I’m trying to figure out if it was an original development or, like many Russian guns, had a prototype in a Western gun. Any ideas?
The Sporting Bookworm's Hermitage 
This is by chance not the twin brother of the MC-22? https://i3.guns.ru/forums/icons/forum_pictures/017928/17928856.jpg
It is also strange that this is attributed to Izhmash – Izhmekh was usually involved in the development of civilian weapons.
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You’ve got a good eye. This is what I suspect, too. (And thank you for noticing the typo. I double-checked the source, however, and it attributes the gun simply to “Izhevsk gunmakers”, without specifying a factory.
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By the way, you don’t know as far as MTs-24/TOZ-87 are associated with MTs-22 (2nd gen)? They are both similar and use a gas-operation system. The fact that they called it by the name of an existing model is also strange.
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1) they are unrelated 2) TSKiB did that (recycling model indexes) all the time
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