Minerva head/assay office mark regional assay office letter M for Schoonhoven.Date letter N for 1973. Maker's mark N10 under Crown for: Niekerk Groothandel in Gouden en Zilveren Werken formely known as; J. Niekerk b.v.( or Fa. Gebr. Niekerk/Firm brothers Niekerk) and this particular mark used 1970/1997
See: http://www.verwoerdceramics.com/silver
Dutch date letters & hallmarks see: http://www.925-1000.com/forum/viewtopic.php?f=5&t=32028