The preliminary study for this, in the same sense and incised, was sold at Christie's, London, 4 June 1860, lot 577, and is now in the British Museum, London (Schnackenburg, op.cit., no. 75). The knife grinder is sharpening the tools of a cobbler in front of his 'underground' workshop similar to that in B.27 (see lot 25), obviously constructed in this way for practical reasons. Schnackenburg dates this plate to circa 1653-60 and Slatkes to circa 1654-60. The geometrical fragment on the reverse of the plate shows the left half of a plate originally used to print the illustration of a half circle in Juan Alfonso de Molina Cano's Descubrimientos Geométricos, Antwerp, 1598. Ostade used the other half of this plate for his etching B.39 (see lot 36 in this sale), which Slatkes dates to circa 1647-53. Ostade's etchings B.12 and B.25 are also done on a plate used for de Molina Cano's book (see lots 10 and 23 in this sale). For further information see p. .. in this catalogue.