Lisbon - [s2e3]

You're likely thinking of the that is a signature of The Professor in the series Money Heist ( La Casa de Papel ).

: While never shown on screen, it likely referenced "Viking Gold" or "Family Tradition" to convince Rafael to return the stolen gold. Rafael’s response to Lisbon was simply, "It's a family matter". [S2E3] Lisbon

If you are asking about a specific piece of related to the character Lisbon (Raquel Murillo), it might be the mystery note from the series finale. You're likely thinking of the that is a