Yes it is an apothecary weight, two scruples, a scruple is 20 grains so two scruples is 40 grains or 2.59 grams. It was made by Henry Troemner of Philadelphia probably in the 1840's. Troemner made weights and balances beginning in 1840 and formed his own company in 1844. His balances were high enough quality they the Department of the Treasury had him make bullion balances for the Mint and assay offices. Troemner died in 1873 but his sons continued the business which still exists today and apparently is still a major producer of weights, balances and scales.
