For those of you who long for the cloud-like ride of Clement Criterium Seta Extras from the early 70s (which, from what I recall, used to cost about $15 for Setas and $18-20 for Seta Extras), it might be useful to know that André Dugast silk tubular tires are now available at World Class Cycles.
http://www.worldclasscycles.com/
They are expensive ($140 each!), but at the same time, you only live once.
Jim Kadonaga
Del Mar, CA