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In some cases, Fighting Fingerprint, Everyone Has a Special Move, or Signature Move (when a specific move is extremely signature to exactly one person).
I'm coming up empty as far as signature other things. I'm a little surprised that tropes like Creator Thumbprint don't have in-universe examples, and there doesn't seem to be any in-universe counterpart that I can find. The closest thing might be Famed in Story like if someone is a famous craftsman or artifact maker considered to be second to none.
^ that's the one for the second part- it's a variant in that the respect comes from a demonstration rather than reputation, but the end result is still establishing Alice is an expert because she impressed Bob.
I'd also use that for the situation where, say, the scholar of magic recognizes that an ancient magic item could only have been crafted by a mage of great skill, or the tracker recognizes that they're pursuing someone who knows how to conceal their trail from anyone but another expert.

Either upon closer inspection of an artifact, when one character with a keen eye realizes that "masterful hands have created/written/woven this" or, likewise "this has the mark of <character xyz>".
Or, if in each other's presence, with one of them having (sometimes accidentally) "revealed their hand" (say, in the presence of novices), but this only being recognized by the other hidden master, leading to a knowing, respectful nod or smile to each other, or professional (but often hidden) counter-move that may be equally unexpected by the opponent.