Lot 50018 – British Guiana – 1853-59 Issue 1c, group of 13 glass

British Guiana – 1853-59 « Ship » 1c issue, the astonishing group of 13 glass clichés, including three negative glass cliché in purple-brown, black and grey (latter has crack not affecting the design), six of the glass clichés in differing shades of vermilion (the target shade), two of the glass clichés dated 4/31 and 6/32 indicating when Sperati undertook his work, one black cliché marked as « a » with the Sperati notation « 22 x 6% x 3’30 » « indicating the temperature was 22°C and he used 6% of a substance exposing it to light for 3 minutes 30 seconds, the vermilion examples with similar notations indicating the process of refining the quality of the impression through the use of varying quantities of substances and light exposure at varying temperatures; a remarkable and unique assembly of glass clichés from this iconic British colony, which includes three negative glass clichés which are valuable and very rare in any territory produced by Sperati. There has been no mention in the literature dedicated to the work of Jean de Sperati on British Guiana, making this lot a highly valuable considering the significance of this country in classic philately.