It's a surprisingly complicated subject. A lot of manufacturers were well known Jewellers, some were retailers, some dedicated to medal production like Klein and Quenzer who originally made watch chains. A definitive list is difficult to achieve as often a new or unidentifiable mark crops up or a cross that doesn't fit into the mold. SOme marks are open to speculation as to who they relate to. There's plenty of reference about and a lot of knowledge on this site ref. makers etc. George's link above, The Kaiser Bunker, is an excellent resource. Glenn.