It's printed on black matte PVC with white and silver scratchable ink. 
PVC makes it possible to write on with chalk and erase, leaving no trace.

The scratch-able ink does leave different traces, depending on the material used to scratch with.  
 
It was printed by Tind (www.tind.gr)
 
All versions measure 50x70 cm. and it's strictly limited to 100 copies in total.

Available for sale here: http://inkblotsilkscreen.bigcartel.com