Portuguese marriage key pendant

This is a one-off, a Portuguese marriage key pendant, circa 1780.  I have had permutations of this type of jewel before set with portraits of Portuguese royalty or pastoral scenes. Sometimes I have seen them sold as pendants with the watch key winder missing. I cannot find another marriage example in any jewellery reference book or museum collection. This original gold key is set to obverse with a watercolour portrait of a young bride, possibly a member of the aristocratic Da Cunha family. She wears coral earrings and a coral necklace for good luck and her hair is adorned with pearls. To reverse, over a flaming pyre of love and beneath a wreath of flowers, a bride and groom clasp hands. The pyre is inscribed Firmeza : firmness, symbolising love which is firm and constant. Both portraits are in a surround of sea-green chrysoberyl, with the gold bead detail typical of Portuguese jewels of this era. It is two inches long and immaculate.