a gold coin, worth 25 shillings; so called from King James I. of England, in whose reign it was struck. See Coin.

We usually distinguish two kinds of Jacobus, the old and the new; the former valued at 25 shillings, weighing six pennyweight ten grains; the latter, called also Carolus, valued at 23 shillings, in weight five pennyweight twenty grains.