Nacre recovered from aulococerids as well as from belemnites resembles that found in recent Sepia and Spirula but differs from that of recent Nautilus.
It is based on the story of the same name by Anatole France in his collection L'Étui de nacre, which was in turn based on a 13th-century medieval legend by Gautier de Coincy, c.
Keytops could be of plain boxwood, or lavishly decorated (as was often the case in northern Italy) with ivory, ebony, mother-of-pearl or tortoiseshell among other materials.