σφραγιστήριον
From LSJ
τέχνη δὲ ἄνευ ἀλκῆς οὐδὲν ὠφελεῖ (Thucydides 2.87.4.6) → η τέχνη απαιτεί κουράγιο, skill without heart is useless
English (LSJ)
τό, A seal, stamp, PLond.5.1657.13 (iv/v A.D.); = signaculum, signatorium, Gloss.
German (Pape)
[Seite 1052] τό, Siegel, Petschaft, Sp.