Quiet Street Antiques of Bath has dated this piece to the 1800s.

The main silvered register plate is particularly well engraved whilst there is a long thermometer to the trunk and a hydrometer to the top, which for some reason (ideas please?) turns using the key and the square just beneath it.
Negretti started producing barometers and other scientific instruments around 1800 and entered into the famous partnership with Zambra in 1850. This barometer pre-dates this.
Quiet Street Antiques of Bath has dated this piece to the 1800s.
Fine antiques at sensible prices
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