Just picked this up.... it`s a racing rear rotor used on some British Super Sport Triumph 675s (interchangeable with Honda rotor). Weighed it last night, 384g (0.95 lb lighter than stock). It`s only 3mm thick, however (and that is the original thickness as I measured both the wear area and the mounting area).
There is another for sale on UK eBay site if anyone is interested:
http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 1405591290