Cyrillic letter Yat with diaeresis in a dictionary by Vladimir Dal.
Yat with diaeresis (Ѣ̈ ѣ̈) is a letter of the Cyrillic script. It was formerly used in Russian, before 1918 when the yat was removed. The letter comes from a yat with a diaeresis.
It represented instances when yat was pronounced like ё (yo).