1. 
   Witness mark
   A material mark placed at a known distance and direction from a property corner, an instrument station or a survey station, as an aid in its recovery and identification.
   Found op http://www.ecy.wa.gov/programs/sea/swces/products/glossary.htm
   
   
2. 
   Witness Mark
   A punch mark or scratch used to position or locate some part in its proper spot. The mark is made on each half of the assembly so that upon reassembly the marks can be lined up.
   Found op http://www.diracdelta.co.uk/science/source/w/i/witness%20mark/source.html
   
   

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