Saw this in a museum yesterday, and thought first that it is a camera of some kind. But google gave hints that it would be a sort of slide projector for showing a roll of slides in 18x24 format on 35mm film? Also I got the idea that it is for kids and made around 1950'ies?
This is a diafilm (film strip) viewer. Definitely a toy construction (as it says on the front - "children's filmoscop"). I would think it has some kind of window on the back, to point it to a light source. Load the diafilm (18x24 frames), look into the lens and get some light from behind. Diafilms were very popular in the USSR, more common than slides. This think looks sooo Soviet built. Must be some military plant in Zagorsk, they could not resist to stamp those stars:)
Unfortunately I could not see the rear as the device was in a vitrine, but all this makes sense, as I hear translation for the Cyrillic Russian text which I can't understand. We also had a lot of these "slide strips" in Finland, they even had a name "raina".
i have one of these, it's a very simple metal film viewer, the back opens up, you load film onto two spools and you look at the light. It is made apparently by two factories, Zavod No. 6 in Zagorsk and Metallozavod in Moscow. The Metallozavod also has a blind for the second eye. I've seen it come in different colors, brown, blue, green, black. I will try to post photos later of mine.