Hi Euser, Town mark Middelburg, late 18th century double headed eagle uncrowned, 1st standard or Grote Keur 10 penningen and 12 greinen or 775/1000 fineness. Year letter Y combined with the Town mark for the year 1798. Maker's mark IWG in a trefoil for Johan Werner Gericke, born in Hildesheim 25th March 1746, registered silver smith in Middelburg 19-11-1782. Died in Middelburg 27th November 1801.
Source; J. de Bree Zeeuws zilver Interbook international B.V. Schiedam 1978