拇印 is read as ぼいん (boin) and means thumb print.
ぼいん
boin
ちょういん
signature
けしいん
postmark
しるし
token (of gratitude, affection, etc.)
めじるし
trademark
やじるし
arrow (symbol)
みとめいん
private seal
しゅいん
red seal
はたじるし
design (on a banner)
しょういん
a seal affixed to a document
こくいん
brand (i.e. a mark of disgrace)
むじるし
unlabeled
じついん
officially registered seal