When is a stamp like a coin?

When it is made of Silver.  It seems the Dutch wanted to go out with a bang when Guilders were to be replaced by Euros.  So the last ever Dutch stamp to be priced in Guilders was cast in Silver. I was sifting thru my pile of stamps when my finger struck the edge of a saw blade in the pile. Turns out these were the metallic teeth of the silver stamp. Makes for a heavier envelope when one corner is weighed down by a silver stamp. 

A bit tarnished - needs some Silvo