A bit of show-and-tell with some peripherally related items - a wooden box with shaped inserts for scales and metal flaps covering the weights. The recessed part in the lid extends about another 3cm into the lid itself, presumably to hold tweezers or some such for picking out the weights. The weights under the main flap are numbered 1, 2, 3, 4, 8, 16, 32 and 64 GN (grains?).

The whole thing is quite compact - the box is about 14 x 7 cm, the "1" weight only 5 mm square, the "32" is 14 mm square. From the shape of the numbers, the 3 in particular, I'd guess it's mid-Georgian to early Victorian, say 1780s to 1840s. If anyone can improve on the dating I'd be very happy to learn more :-)