Belgian Congo – 1887-94 Second Issue 10fr, assembly of 38 items, comprising one negative master glass cliché with the surround and the tablet denomination handpainted on reverse in blue with the purpose of avoiding the light to enter laterally in the following step, five glass support clichés showing different intensities of impression, eight clichés on celluloid mainly in black and vermilion to create better contrasts, including one with part of additional impression disposed sideways, two essays on paper with blank denomination and one with part of further impression sideways; the part dedicated to postmark features cds’s of Boma and Matadi, with eight glass clichés of which five are negative, and eight essays on paper with numerous annotations by Sperati, which also numbered these essays and dated in Dec-44 and Jan.-45; along with six cutouts from auction catalogues used by Spearti to trace the cancellations, which are highlighted in black. A sensational and unique group, with no more clichés in the « Ultimate » collection or in the Postal Museum in Paris; nor the negative and nor the cliché in possession of the B.P.A. are dated, with this much more extensive assembly of preproduction artifacts providing dates in 1944 and 1945.