Neutral Yer

Neutral Yer (Majuscule: Ꙏ, Minuscule: ꙏ) is used in transcribing documents when it is hard to tell the difference between a Ь and a Ъ. It was common in Late Medieval Russian archival materials and scripts.

Cyrillic letter Neutral Yer
The Cyrillic script
Slavic letters
А А́ А̀ Б В Г Ґ Д Ђ Ѓ Е Ѐ Ё Є Ж З З́ Ѕ И І Ї И́ Ѝ Й Ј К Л Љ М Н Њ О Ō П Р С С́ Т Ћ Ќ У Ӯ Ў Ф Х Ц Ч Џ Ш Щ Ъ Ы Ь Э Ю Я
Non-Slavic letters
Ӑ А̄ А̊ А̃ Ӓ Ӓ̄ Ӕ Ә Ә́ Ә̃ Ӛ В̌ Ғ Г̑ Г̣ Г̌ Ҕ Ӻ Ғ̌ Ӷ Д̣ Д̆ Ԁ Ӗ Е̄ Е̃ Ё̄ Є̈ Ӂ Җ Ӝ Ҙ Ӟ З̌ З̱ З̣ Ԑ Ԑ̈ Ӡ Ӣ И̃ Ҋ Ӥ Қ Ӄ Ҡ Ҟ Ҝ К̣ Ԛ Ӆ Ԯ Ԓ Ӎ Ӊ Ң Ԩ Ӈ Ҥ О́ О̀ О̆ О̂ О̃ Ӧ Ӧ̄ Ө Ө̄ Ө́ Ө̆ Ӫ Ҩ Ԥ Р̌ Ҏ Ҫ С̣ С̱ Т̌ Т̣ Ҭ У̃ Ӱ Ӱ́ Ӳ Ү Ү́ Ұ Х̣ Х̱ Х̮ Х̑ Ҳ Ӽ Ӿ Һ Һ̈ Ԧ Ҵ Ҷ Ӵ Ӌ Ҹ Ҽ Ҿ Ы̆ Ы̄ Ӹ Ҍ Э̆ Э̄ Э̇ Ӭ Ӭ́ Ӭ̄ Ю̆ Ю̈ Ю̈́ Ю̄ Я̆ Я̄ Я̈ Ԝ Ӏ
Archaic letters
Ꙁ Ꙃ Ꙅ Ꙇ Ꙉ Ҁ Ѻ ОУ Ꙋ Ѡ Ѽ Ꙍ Ѿ Ꙏ Ѣ Ꙑ Ꙓ Ꙕ Ꙗ Ѥ Ѧ Ꙙ Ѫ Ꙛ Ѩ Ꙝ Ѭ Ѯ Ѱ Ѳ Ѵ Ѷ Ԙ Ꙟ Ꙡ Ꙣ Ꙥ Ꙧ Ꙩ Ꙫ Ꙭ ꙮ Ꚙ Ꚛ Ԁ Ԕ Ԗ Ԡ Ԣ Ҧ Ꚋ Ꚁ Ꚅ Ꚍ Ꚕ Ꚏ Ꚗ Ꚃ Ԃ Ԅ Ԉ Ԋ Ԍ Ԏ Ԇ Ꚑ Ꚉ Ꚇ Ꚓ Ԟ Ԫ Ԭ Г̧ Г̄
List of Cyrillic letters Cyrillic digraphs

The appearance looks like a Yer with a hook on the top.