The snake motif was a popular symbol of eternal love, as it showed the snake ingesting its own tail, therefore representing eternity. Much thought has been given to Queen Victoria for popularising the snakes (as given to her by Prince Albert), however, this motif predated her usage by over fifty years.
This snake with its foiled garnets and green paste eyes is a supreme representation of the serpent motif and defies the common construction of the time. For its construction (c.1820), This piece should show a more rectangular shape, however, as like eye portrait jewels, it retains its own shape to conform to its style.
This makes the snake rounder and more organic in its shape. The 1904 date is discredited very strongly, and there is no constructional, artistic or popular credence given to it being contemporary for this time. Obviously, the date is added later to the piece.