Unidentified - Silver Coin / Token German Empire (1871 - 1922) (Id: Likely Postcard Pendant)

It isn't an altered coin - the obverse (the eagle-side is the obverse of these coins) is engraved a little too crudely, and at the bottom, where there should be two identical letters (eg. "A-A" or "G-G", there are two different letters ("B-M"), which I assume would be the initials of the manufacturer. Given the design, I would assume it's a made-for-jewellery piece, later broken off (perhaps during post-war hard times to be spent as money).

On the reverse, we have what appears to be a "postal stationery" postcard (the only words I can read are the top two lines, "Deutsches Reichspost Postkarte"), perhaps something like this example on Wikimedia. Presumably it was given to a son/husband/fiancee/boyfriend, perhaps someone who had gone off to war, reminding them to keep in touch by writing letters.

This is a private issue made by B. Meyer in the size of a 20 pfennig.