Lot 50621 – Switzerland, Winterthur – 1850 2 ½rp, glass support

Switzerland, Winterthur – 1850 2 ½rp, glass support cliché of background with reversed image, showing what is red in the original stamp, with notation “cuivre sans verni” (unvarnished copper) and indication about the light “B.L.” over the screen which was used for the two minutes and thirty seconds exposure, “2’30″”.