negative squared latin capital letter a symbol.
Copy and paste this emoji:
symbol
A button (blood type) was assigned codepoint in Unicode 6.0 on 11 October 2010.
A button (blood type) was included in Emoji 1.0 on 04 August 2015.
🅰 U+1F170
:a:
㊗ Japanese “congratulations” button
🈺 Japanese “open for business” button