Variant of the Cyrillic letter O, used in a Book of Psalms manuscript from 1429. It is only used in one word: mnogoočitii, an Old Church Slavonic meaning “many-eyed” in the phrase “many-eyed seraphim”. The proper way to draw it is with ten Os.

The origin of this odd letter can be found in the Monocular O, used only for the word “eye” in birch manuscripts since the 14th century.

There’s also the Double Monocular O for “eyes”

Let’s mention the Binocular O, for “eyes” as well.

“The crossed o is primarily used in the word ꚛкрест (around, in the region of) in early Slavonic manuscripts,[1] whose component крест means ‘cross”.

12th century birch bark letter from Novgorod