Alexandra Feodorovna wore a similar nuptial crown, to the one that inspired these clip-on earrings, on her wedding to Tsar Nicholas II in 1894. They have 47 rhinestones set into a silver-plated half crown that has been antiqued. Also, they hang from a hinged ball and loop clips. And, their overall length is 1 and 1/2 inches (38mm). From Museum Reproductions.
Note: See the crown, which is on loan to the Hillwood Museum, by clicking here.