Coin-related Term: Mass

The actual mass of the coin when struck at the mint and before wear takes place. Specifications are laid down as standard by the issuing institution. Measured in grammes (abbreviated to g).

Most catalogues list the "weight" of a coin and not mass. Technically speaking though, what should be measured is mass and not weight.

However, since most collectors tend not to leave Earth too often (in which case the mass of their coins would remain the same but the weight would become negligible in micro-gravity), the two terms seems to be interchangeable for practical purposes.