South Africa 1925 Airmails Composite Proof Sheet, Mauve, Signed

1925 Airmails 1d - 9d (SG 26-29). COMPOSITE IMPERF PROOF SHEETLET IN MAUVE, all four values, SIGNED BY DESIGNER. The sheetlet reconstituted of separated upper and lower horizontal pairs (1d & 9d / 3d & 6d) on gummed unwatermarked paper, large part OG. Each pair signed in margin "AJ Cooper", the designer of the stamps. Exceedingly rare proofs, quite likely unique with signatures thus, a showpiece for this Airmail issue. Arthur Cooper, a former employee of Waterlow & Sons, London, had joined the Cape Times Ltd who printed these airmail stamps from his design. See additional images.