Seven ranks, seven metals, and seven spirits holding two titles
The Goetia classifies its spirits twice: in the entries and in an appendix that lists all seventy-two by rank and gives the metal for each rank's seal — gold for Kings, copper for Dukes, tin for Princes, silver for Marquises, mercury for Presidents, copper and silver for Earls, and lead for the Knight. The lists do not always agree; seven spirits appear under two ranks. The catalogue follows the appendix, since words such as Knight and King also occur descriptively in the entries without granting a title.
Sources (1)
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Lemegeton
, The Goetia: The Lesser Key of Solomon the King
— Classified List of the 72 Chief Spirits, note
“It will be remarked that several among the above Spirits possess two titles of different ranks; e.g., (45.) Vine is both King and Earl; (25.) Glasya-Labolas is both President and Earl, etc. "Prince" and "Prelate" are apparently used as interchangeable terms.”
The edition remarking on its own inconsistency. Crowley adds a further speculation there — that Earls' seals should probably be iron, since otherwise Mars is left out of the seven planetary metals — which is his reasoning and not the book's, and is not seeded as fact.