Charles-Melchior Descourtis (1753-1820 )Frédérique Louise Wilhelmine of Prussia, Princess of Orange Nassau. Stipple engraving and aquatint after Tozelli, under the direction of Hentzi. 315 x 430. Le Blanc, I.F.F. not described. Printed in colours. Exceptional trial proof with the names engraved in point, before the letter, the background drawn in azure blue, formerly washed and re-glued, with persistent traces of glue and small restorations to the edges of the folio on the verso (including a short tear perceptible at the right edge). Small margins. Very rare.