Antique Tankard Or Not.

I found this antique-ish looking mug at a yard sale. A friend told me it was silver since silver tends to darken over time. If true does this mean this is silver?

I found a hallmark at the bottom of the piece that says WMF Sinn with an angel holding a balance. I could not find the maker info other than WMF is German but no info on the SINN connection. sorry I could not take an adequate picture of the hallmark since its faded and hard to read.

Is this an antique or mass produced recent product? any value? is there a site I can go to to find out more about the maker? any info is appreciated.

thanks
Hexster
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