Note about rules signed LENOIR

Etienne Lenoir and his son Paul-Etienne were the first in France to produce slide rules in quantities in their workshop, from about 1820. Paul-Etienne died in 1827 and his father in 1832.
The inventories after death show that their equipment was sold in 1827. Mabire (of whom little is known) first took over the business, then Francois-Fuscien Gravet in 1839. They could sell under the signature Lenoir.
But in 1851, a judgment of the commercial court of Paris required that Gravet sell its instruments under the brand Gravet-Lenoir.
That is why the signature "Lenoir" only indicates that the instruments were manufactured before 1851, either by Lenoir, or by Mabire, or mainly by Gravet.
Some rules are signed both Lenoir and Gravet-Lenoir. One can therefore conclude that they were manufactured shortly before that date, and sold after, as Gravet had to rectify his trademark.

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