A 1923 2c Harding Memorial horizontal strip of three, featuring the extremely rare perforated-11 Scott 613 error, is the leading lot in a collection of exciting US specimens at the Michael I Casper Rare Stamp Auctions event on April 26.

The three stamps, which formed positions 56, 57 and 58, have all been lightly cleaned. There is a short perforation at the top of position 58.

With an estimate of $200,000 and the current price from pre-auction bidders standing at $125,000, it is sure to have stamp investors taking notice.

The Harding Issue was created by noted stamp designer Clair Aubrey Houston. It was produced within just weeks of the US president's death in August 1923, following a heart attack while on an Alaskan voyage.

This rare strip of memorial stamps is expected to achieve $200,000

Houston used a copperplate etching of Harding, incorporated into a modified form of the Fourth Bureau Issue frame.

Rounding out what promises to be an auction to remember is the controversial Vancouver Sanction collection.