Maria Duval explains the Seal of Mercury is specially

Please note that for this the seal of mercury to exercise its power properly, it should be associated with an object made of bronze and be stored in purple-coloured surroundings like being wrapped in a deep red silk or woollen material.
Maria Duval further explains that the seal is an appropriate protection for those who are on long journeys, or for doing business abroad with foreigners. It aids also when you are trying to learn a new language, studying for exams, or improving one's memory. Health-wise, the Seal of Mercury can relieve respiratory or muscular defects.
At Peace.
PS:
Surprise! www.mariaduval.com now goes to www.mariaduval.net.
Glad.