That's a nice website to browse through. Interesting how they have "the only known example" on some stuff. Whether they actually are the only known examples would of course be difficult to impossible to prove, but it is interesting to think that with the internet and all, not a single other has been seen, to their knowledge. The only thing I'd be slightly skeptical of is how the items look in person compared to the photos. The photos are more in the Heritage Auction style - very edited and "perfect" looking, and at least one of the photos is from Heritage. Personally I'd ask for a more natural photo if I were interested in buying anything. It really is a nice website and it's cool to see all the great stuff they have.
