I once found, in a second hand birding book (Collins Guide / Fågelguiden), a "congratulations to your degree"-card with an embossed crown on it, signed by Frida

I once found, in a second hand birding book (Collins Guide / Fågelguiden), a "congratulations to your degree"-card with an embossed crown on it, signed by Frida + Ruzzo. Some additional details lead me to the conclusion it was written by Anni-Frid Lyngstad of ABBA. (Ruzzo was Frida's late husband, who was prince of House of Reuss)