Lot 50106 – Spanish Colonies, Río de Oro – 1907 4p error of colour se-tenant with 3p, group of 13 items

Spanish Colonies, Río de Oro – 1907 4p error of colour in se-tenant pair with 3p, group of 13 items featuring the typographic and photolithographic process, the former featuring a highly valuable copper plate, two die proofs on pelure paper including one with annotation « press. 6,5 » which was probably related to the set up of his press, three essays in green on wove paper including one with incomplete impression and one over-inked and excluded with a blue crayon cross (dated August 1926); the photolithographic process is illustrated by an important master negative cliché on film with handprinted surround to avoid the light to diffuse laterally, with incidentally the serial numbers on the back of the stamps which have been also transposed, six glass support clichés (three including a portion of a third example which was a 3p) including one which had not a sufficient exposure (« expo. insuff. 5’30 » « ) despite 5 mins 30 secs in February 1935, this cliché and two others present a part of a third example of 3p value. An incredible and unique lot demonstrating the usage of two different printing processes and including a copper plate, the only one known for Río de Oro and being a very rare artifact in the Sperati archive; the B.P.A. Sperati I states to have only seen a proof of impression of a single 4p+3p se tenant pair as the previous proof of this pair recorded, which evidently indicates the importance of this lot and its discovery.