About: http://webisa.webdatacommons.org/122829235

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	JD - your point is a very good one - the 503 model sold for some time before they added that restrictor so it must be capable of performing without it being shut and necessary therefore only for chimneys with very strong draught.
http://www.w3.org/ns/prov#wasQuotedFrom	nepacrossroads.com