Literature. 'Die John R. Boker Jr., Sammlung Altdeutsche Staaten', Vol. I–II and III Prussia, Heinrich Köhler-Auktionen, in three volumes in two slipcases, No. 79 of the limited edition, imitation leather with gold embossing. Sold out and rarely offered on the market – very sought after. Reference work of enduring value. Approx. 7 kg.