"Old Proportion Compass / Half-foot From A Collection King"
18th century folding square for mathematical calculation produced and distributed by the LANGLOIS dynasty in Paris Claude LANGLOIS 1690/1756 Master founder of mathematical instruments and King's Engineer active from 1730 to 1756. this engraved brass scientific instrument has two assembled branches with a tab that forms an unfold square. is signed by LANGLOIS in Paris at the Galerie du Louvre (according to the model of this signature and the address, the square can be precisely dated to 1750/56. in good condition. Closed size 17 cm x 2.15 cm. weight: 127gr 
Le Magazine de PROANTIC
TRÉSORS Magazine
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