For the Only Watch 2013 charity auction, Patek Philippe has produced a one-of-a-kind version of the discontinued ref. 5004 in titanium called the 5004T. While Patek Philippe has produced titanium watches in the past, they are exceedingly rare and none that I can find have been produced as part of an series.
The article Patek Philippe Titanium 5004T For Only Watch 2013 (2,950,000 Euros) first appeared on aBlogtoWatch and was written by Ariel Adams.