[spiros]

Well, it is pretty much a standard Turkish letter :)

The Turkish alphabet (Turkish: Türk alfabesi) is a Latin-script alphabet used for writing the Turkish language, consisting of 29 letters, seven of which (Ç, Ğ, I, İ, Ö, Ş and Ü) have been modified from their Latin originals
https://en.wikipedia.org/wiki/Turkish_alphabet