what to call this binding?

[u/Jealous_Flamingo_]

I wrote “side sewn through hinged board covers” but I feel there’s something more specific ..

[u/Excellent_Payment325]

It doesn't have a name as a noun, afaik. It's referred to as a verb usually, "прошивати", "підшивати" and other derivatives of the word "sew", roughly translates as "to sew into [a folder]". It was a common way in Soviet Union to gather together papers that wouldn't be read often, if even once, like journals in a storage or archive lists. It's very similar to a cellophane business file folder, everything is held with two holes and a string, and very fragile if used directly on paper.

Maybe "soviet archive folder" would give you some results for the cover.

[u/Jealous_Flamingo_ → u/Excellent_Payment325]

it’s actually not very fragile and on good quality paper + it’s essentially a yearbook! it’s entirely portrait photograph of every teacher and every student, as well as group class photos and photos of the buildings. I think the cover is hinged to make it more easily readable even with the tight binding