Etching, engraving and open-bite, 1749-50. 417x564 mm; 16 1/2x22 1/4 inches, wide margins. Fourth state (of 6); Robison's second edition, second through third issues, printed from the early 1760s to the early 1770s. Proprietary watermark. From the Carceri d'Invenzione. A superb, dark, richly-inked impression with very strong contrasts and no sign of wear. Robison 38.