Antique 1850-1870 Copper Relief Plaque 5.25" by L. Birnbaum 'Lohengrin & Elsa'.

The scene depicts Lohengrin, a character in German Arthurian literature. The son of Percival, he is a knight of the Holy Grail sent in a boat pulled by a swan to rescue a maiden who can never ask his identity. Richard Wagner's opera 'Lohengrin' of 1848 is based upon the legend

A rectangular version of this plaque was made for fitting to the top of wooden boxes, a few can still be found, but this is the only circular version I can find