I is a letter used in almost all modern Cyrillic alphabets with the exception of Belarusian, where it is replaced by І.
И, from Alexandre Benois' 1904 азбука.
In early Russian typewriters like this one, there was no key for the digit 1, so the capital І was used instead. Following the Russian alphabet reform of 1918, a 1 key was added.
The Bulgarian Cyrillic alphabet is used to write the Bulgarian language. The Cyrillic alphabet was originally developed in the First Bulgarian Empire during the 9th – 10th century AD at the Preslav Li
Cyrillic Script Monument at the Bulgarian base in Antarctica