An unfinished brass protractor, Probably Italian, in the manner of Giacomo or Dominicus Lusuerg, late 17th or early 18th century

AN EXCEPTIONAL RARITY: AN UNFINISHED SCIENTIFIC INSTRUMENT

A truly unusual survival: an unfinished protractor, finely crafted in brass but with several mistakes in the scale division.

The style is remarkably similar to that of the Lusuerg family of instrument makers, active in Rome from the 1670s to 1740s. The extended ‘tangent’ arm with a decorative finial is characteristic of the Lusuerg workshop – though the engraving on finished Lusuerg’ pieces is of a very high quality and is here lacking. This could either be a trial piece, or an imitation.

The chances of an unfinished instrument surviving even a single day are very low – so for this instrument to have survived more than three centuries is exceptional.

Unfinished instruments reveal much about the process of engraving: here we have a glimpse of the order in which the scales were engraved, with the main degree markings laid out first (these are neat but by no means perfect) followed by a linear scale at the bottom of the instrument, and the beginnings of another set of scales inside the semi-circle. The latter may even reveal the order in which division lines were struck off for dividing the circle, as it is not only incomplete but also divided at the 30th, 33rd, 36th, 40th, 45th, 52nd, 60th and 62nd degrees.

Fine condition: housed in a custom-made clamshell box with marbled paper. 118 x 77mm.