Compass by Jeune Rochette 

This unusual compass is graduated in 400 degrees ( Gons) which I think was an attempt in early metrification of the whole circle that allows 100 degrees in a right angle.

The compass face is inscribed with the makers name.

" Rochette J[eu]ne / au Grifon / Quai de l’horloge à Paris"

Jeune Rochette was a sole trader between 1817 to 1845 and this compass would be circa 1820s.

Background:

By 1808, Marie Putois had formed a partnership with Gaspard Rochette, who was known as Rochette Jeune ( Rochette Junior) as his father Rochette Pere had operated a similar shop in the area.

Gaspard Rochette ( Rochette Jeune) became the sole owner of the " au Griffon" business by 1817 and was listed in business directories until 1845

( Ref: http:microscopist.net)

Upon further research this instrument is a Boussole a' Eclimetre

I have found two definitions for Eclimetre:

- An instrument to be held in the hand for measuring the zenith distances of objects near the horizon.

- A survey instrument used to measure the difference in level between two points, to measure the slopes.

The measurement of the vertical angle was designed to be very accurate as it has a vernier scale.

This compass would be circa 1820s.

The name of the first owner " F. Delteil" is engraved on the side plate. I cannot find any details on the WWW for this owner.