Gubernatorial Seal of Mêlée Island

From Monkey Island wiki

The Gubernatorial Seal of Mêlée Island is an item used to represent the power of the office of Governor of Mêlée Island and presumably the entire Tri-Island Area. It appears only to be a symbol but it also secretly possesses a unique voodoo power, which remains the best-kept secret of the Caribbean for years.

Elaine Marley gives the seal to her husband Guybrush in Escape from Monkey Island to convince the Harbor Mistress to let him take a ship from her docks. On Lucre Island Guybrush shows the Seal again at the Second Bank of Lucre to demonstrate his right to retrieve the Horatio Torquemeda Marley's safe-deposit box. Later, when he returns to Mêlée, Guybrush can try to use the Seal to impress the patrons of the Lua Bar but Elaine will come and take it back from him. Even if he doesn't use it she will still recover it before he leaves for Jambalaya Island.

After Herman Toothrot recovers his memory and remembers that he is H. T. Marley, he explains how, even though he revealed many of the Caribbean's secrets to Ozzie Mandrill twenty years ago, including the secret of the Ultimate Insult, he did not divulge to anyone the fourth ingredient required to make the talisman, which not even the spell created by using the Marley heirlooms properly shows. The fourth piece is the gubernatorial seal, one of which he still has, allowing Guybrush to complete the transformation of the Giant Monkey Head into an enormous Ultimate Insult. Unfortunately, Ozzie and LeChuck find Elaine's gubernatorial seal and figure out its role at about the same time, thus empowering their Insult and allowing their plan to move forward.