VERY FINE AND CHOICE MULTIPLE. THIS IS THE ONLY RECORDED SIDEROGRAPHER'S INITIALS BLOCK OF THE RARE GROUNDED PLANE VARIETY.
The true Grounded Plane stamps, in which the wheels of the plane break through the top of “Cents”, come from various portions of three different sheets. The discovery sheet was owned and broken up by John Klemann Jr. of Nassau Stamp Company. A second sheet was discovered in 1946 and sold in the Thomas A. Matthews sale (H. R. Harmer, Nov. 4, 1964), where it was purchased by Georges A. Medawar, publisher of Sanabria Airmail Catalogue. In Linn's Stamp News (April 21, 1986), Joe Kirker published his research identifying a third sheet as the source of the Grounded Plane variety.
The block offered here comes from the Matthews-Medawar (Sanabria) sheet and shows a strong downward shift. There is no record of another Grounded Plane with the siderographer’s initials.
Ex Matthews, Medawar, "Aurea" (Golden) and Blumenkopf