An extremely rare block of 20 1898 $2 Trans-Mississippi stamps will be sold at Robert A Siegel on March 17-18.
It's valued at $150,000-250,000.
The block is the second largest multiple of the issue and is offered in mint, never hinged condition. The six stamps in the centre are perhaps the finest specimens on the market.
The auction house explains: "There are no known full panes of 50 of the $2.00 Trans-Mississippi -- the only denomination of the series for which no full panes remain.
"There exists one block of 25 from the lower half of the right pane, which is the largest known multiple.
"This margin block of 20…has not been offered at auction in nearly 50 years, last appearing in the Siegel 1968 Rarities of the World sale, where it realized double the then current catalogue value."
A broad selection of modern errors will also feature.
A used 1938 $5 Calvin Coolidge presidential issue (or Prexie) will provide the headline lot of this section, with a $7,000 estimate.
The stamp displays much richer colours than the normal issue. This is one of only two known used singles (there is also a used block).
An important collection of transatlantic stamps from the Steven Walske collection will be sold at Siegel on March 16.
Please sign up to our free newsletter to receive exciting news about postage stamp auctions.