Ahahahaha no. Have no never wondered why standards bodies (which decree official weights and measures) are operated by governments? Many times throughout history, measurements of everything from land area to the standard weight of coins have been adjusted by governments to suit their policies (sometimes in the interests of fairness and trade, sometimes in the interests of refilling the treasury or paying an army).

Certainly, one can turn to science and make objective statements about both mass and purity. But unless you have melting facilities and deal in raw metal (rather than stamped coins) there is no advantage in this. As a hypothetical sovereign individual, you'll lose out when trying to trade raw metal because without the word of an independent (and government-licensed) assayer the buyer will discount the value of your lump'o'gold to allow for the possible unreliability of your claims about purity and weight. Most people don't have the facilities to assay precious metals themselves, so they rely on a third party to certify such claims; the implied social contract stamped into a coin or ingot has much greater value than the actual metal itself.

Please, look into some history of money. currency abuse is not a recent phenomenon by any means.