About: http://webisa.webdatacommons.org/9292934

Property	Value
http://www.w3.org/1999/02/22-rdf-syntax-ns#type	http://www.w3.org/ns/prov#Entity
http://www.w3.org/ns/prov#value	In at least one implementation, the bottom layer 210 is a metal plate, such as a steel or aluminum plate having a thickness of approximately 2 mm.
http://www.w3.org/ns/prov#wasQuotedFrom	google.com