This is a Gorget / Ringkragen der Stadtwehr Bremen (early type!) (Bremen City Police).
In use in the early 1920’s.
This is the first type (#645), which can be seen by the chain-holes, these were only present on the first type of shields, later these holes would be replaced by an outfacing pin to hold the chain.
The gorget has been painted black, collectors lore tells that this was done to be less visible during night patrols, in how far this is actually true has to be examined more to out opinion, but it seems at least plausible. It’s a nice original shield with relatively low number.
Not that easy to find, and it would a great display piece in a collectors cabinet.