Germany 1 pfennig 1906 [opgelost]

Hello, in the batch of old German coins I found a strange 1 pfennig 1906. It's the same size as all "brothers" but looks enameled, with strange colouration and wider rim. Maybe counterfeit? Still, who would be so stupid to produce the smallest coin in circulation? I'm adding photos with 1906 in center and all the rest for comparision.

Regards Defi

It is just in worse shape through longer use and maybe someone cleaned it too in recent time.

Yep, that was my second idea...