ectypal.net

Seals... are distinguished from signs by the fact that they do not just bring the invisible matter to mind but also validate and confirm it. Inasmuch as there is so much deception and falsehood in the world, all sorts of means are used to distinguish the true from the false, the genuine from the spurious. Thus a trademark serves to authenticate and guarantee the genuineness of a manufactured product, a gauge to determine the precision of weights and measures, a mint to measure the true value of money, and a seal to mark the authenticity of documents.

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Seals, accordingly, are always means for the purpose of guaranteeing the genuineness of persons and things or protecting them from violation.