Beautifully engraved with the scale Demy Pied de Roy on one arm and a second scale (eschelle) with maker’s signature on the other arm. The end of the square has a notch which accommodates a plumb bob string for leveling. The two holes were likely made for either mounting on artillery or for installing brass sights.
Michael Butterfield was an English Instrument maker born circa 1635 who is believed to have immigrated to Paris around 1663. He initially set up business in rue Neuve-des-Fosses, faubourg Saint-Germaine and by 1685 had relocated to a workshop on the Quai de l’Horloge. Butterfield was appointed Ingenieur du Roi (Engineer to the King) and was a member and juror of the Corporation des Fondeurs. He was also an author who published several tracts on his innovations. Amongst Butterfield’s patrons were the French Royal Court, the Royal Academy of Science, the Paris Observatory, and the Russian Tsar Peter the Great. He made all types of instruments including very fine drawing and surveying instruments which may be seen in many museums, though he is probably most famous for the pocket sundial with adjustable gnomon known as the “Butterfield dial”.
A similar square is in the Hermitage collection and a few examples of similar holes/sights mounted onto mathematical instruments:
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Instrumentum is based in the United States and specializes in high quality 17th and 18th century scientific instruments for architecture, mathematics and navigation. We have collected antique instruments for over 20 years with a focus on early and rare European architectural drafting sets, dividers, and rules. Please check regularly as new additions are made and prices may change. If you are interested in something particular please contact us at firstname.lastname@example.org.