For details on this piece, see Crawforth Sovereign balances figure 25 where it is described as very rare.
This is the first one we have offered for sale. It is made of brass with iron hinge screws, 119mm. long and only 9.5mm high when folded.
This example looks like a halfway pieces between the folding balances of the early 1820’s and the standard rocker balances.
It tests a sovereign and half sovereign – I have tried and it works!