Please, help !!! What is it ? - Screwback from a Iron Cross 1st Class ? manufactured by ....... ?
There are brands: the mermaid (undine,siren), a lion with one or two tails, the horseman with a board. On a board a letter "B". More to the right below - small swastika, three crowns or flowers ???. More to the left below may be LDO Maker "L/10" - Deschler & Sohn, München ???
Photo I apply: