Charlemagne had his seal embossed in the pummel of his sword, and used it to seal his letters, which he would then hand over to a courier, saying, “These are my orders.”
He would then show his sword, and add, “And here is what makes my enemies respect them.”
Edmond Guérard, Dictionnaire encyclopédique d’anécdotes (Paris: Firmin Didot, 1872), Vol. 2, p. 352 (Nobility.org translation).
Short Stories on Honor, Chivalry, and the World of Nobility—no. 415