Puckerings has dated this piece to the 1860s.
The rear of the balance is where the signature for Sampson Mordan, London can be found; the creme de la creme of scale manufacturers.

The four original weights sit to the front, marked F, 1/P, 2/P and 4/P. The P refers to "Postages" which were in 1/2 oz units used from 1840 to 1871. The smallest marked "F" is a 1/4 oz unit used for foreign mail routed from England via France. This makes this example a mid-nineteenth century piece dating to c. 1850/1860.

Looks like there was a label originally on the underside, probably for the retailer affixed with four screws. An absolute gem in excellent condition measuring 6 3/4" x 4 1/2" x 3 1/2" tall.
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Item 41363
Puckerings has dated this piece to the 1860s.
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