My first long answer was not taken, my second short answer was taken without login but as a "guest". The new subdivision "without photo" doesn't require a login! So I try again without login.
Halfmoon stands for silver, the crown for the German Empire, 800 for the purity. If it is a unicorn, the maker is: Gebrüder Kühn, Schwäbisch Gmünd, Germany (Gebrueder (=Bros.) Kuehn, Schwaebisch Gmuend) founded in 1860 and still existing. Look at
http://www.kuehnsilber.de" onclick="window.open(this.href);return false;
Regards silverfan