Help to identify - Rostock obol ?

[aidab]

Hi

This piece weights 0,3 gr. and it's diamm. is 11-12 mm. May be an Obol or 1/2 Pfennig

I guess it it is a Rostock coin, but this piece is undated and I,m not sure about if tthe letter of the obverse is an h or an R

[ischbierra]

or a "n" for Northeim