This is a metal cup (I suspect steel from the weight). See images.

The outside has only the crest and the word “Landkreisheilbronn”.

There is an interior hallmark with a diagonal key (facing upwards) with a diamond handle, surrounded by the initials AW. It has a second hallmark above that with what appears to be an angel of justice (sword and balance) with the initials AW.

Dimensions:
~115 mm tall
~85 mm diameter top opening.
~60 mm diameter bottom
387.8 grams