Don't know but a nice Belgium coin. Leopold II - I lived there for 4 years and often found older pennies just on the street because they were worthless as spending money after they got the Euro.
Totally wild, unsubstantiated speculation: inspector's stamp for a rifle stock. DB = the inspector or arsenal, 37 = the year. The stamp is fairly large size as are the letters, but they appear blunt and not sharp, which makes me think they were not intended for metal. That stamp would have made a nice impression on hardwood.
If this were true, then I suppose the year could only have been 1937, since the host coin is from 1870 (too late for an 1837 stamp- unless an old stamp was lying around post-1870...) This may be an unsolvable riddle. But those are fun sometimes.
The letters in the cartouche of the countermark look more like the logo of the "Deutsche Bundesbahn"?
Hmm, Deutsche Bundesbahn (1949-1993) had a logo that was somewhat similar, and Deutsche Bahn (since 1994) uses something like that too. Both without the number below. But I don't really see any reason why they, or Deutsche Bank, would counterstamp a Belgian coin from 1870. Christian
Another observation that may or may have any relevance. The stamp looks like it's been there for a while, but the letter style looks more modern. 1950's or 60's at the earliest? I can't recall seeing letters with style on older counterstamps. But why would a modern counterstamp be on an 1870 coin?