It's said only two sets of these Regular issue small die proofs exist - and one's in the Smithsonian:- All philatelists' eyes have been on Spink Shreves' three-day July 2010 Collector's Series Sale this week, which wrapped-up on Friday (July 23).
Among the US sale's highlights was a complete set of three 1c-$5.00 1902-03 Regular issue Panama-Pacific small die proof stamps.
These proofs were prepared in 1915 for display at the Panama-Pacific Exposition (hence the moniker "Panama-Pacific" small die proofs).
It's widely believed that only three-to-five examples of each proof were ever made. However, Spink Shreves' experts claim to known of only two complete sets extant - of which this is one.
The other set can be found in the Smithsonian collection - although this set is also of remarkable provenance, having formerly belonged to the Kirkpatrick collection.
Each of the three proofs were sold accompanied by a 1985 PF certificate. They boast strong colours, trivial mounting translucencies and were billed as "very fine" in the sale.
In the end, the set of three stamps realised $23,000 - and will prove an exceptionally rare and historic addition to the lucky buyer's collection.
Spink Shreves' sale took place between July 21-23.