Once very common and still found on flea-markets and in thrift stores, the pocket spring balance. In this instance, a Hughes Pocket Balance with the scale marked in kilos.
Above the legend stating it is a Hughes Pocket Balance, there is the knot and arrow logo of Salter. Near the bottom of the faceplate, it states 'patent'. And indeed this is a patented construction for a low-cost mass-manufactured pocket spring balance.
The patent was applied in Britain (granted as British patent 800 of 1884) and in several other countries. Inventors are John Hughes and Thomas Bache Salter, assigning to George Salter & Co. of West Bromwich - makers of spring scales since the 1790s. The drawings of e.g. the Canadian patent 20,397 show exactly the clever construction of the item above.
The single metal sheet at the back forms the frame, with the several shaped pieces slotting into and onto the spring and frame like a sliding-puzzle. Only a few rivets needed to create a working unit, no brazing or soldering.
The top of the frame sheet is shaped with 'flaps' as shown also in the above figures from the
US patent 390,522 applied for in 1884 and issued in 1888. These flaps are folded over to form the top wall of the frame, slotting into the top-eyelet that is attached to the spring. Even though this specimen was heavily corroded, the flaps are visible.
The construction of these pocket balances has not changed much since 1884 - they are still being made new today with the same design and construction.
This makes these items also quite difficult to date, it is hard to estimate when a specimen was manufactured.
The marking of Salter's pocket balances seems to have changed from Hughes to Salter over time, for example in the picture in
a 1921 advertisement the faceplate is marked Salter. Of course not certain if all products changed from Hughes over to Salter, or if it perhaps varied per type or batch even.
The knot and arrow trademark was registered in 1884, so that also does not narrow it down in any way. Specimens with hollow 'pop'-rivets instead of solid rivets would however be more modern, e.g. 1950s or later. A post-war item would also be expected to have a 'made in England' marking.
All this merely narrows the date-range down to anywhere between 1884 and perhaps 1920-ish. The style of engraving on the brass faceplate is fits that range - for example the below Salter-marked specimen with a more modern-looking engraving is likely to be from the 1920s or 30s.
Impossible to date exactly, this slightly battered Hughes Pocket Balance probably dates from around 1900, with about 15 years uncertainty either way.
A proven and timeless design :-)
