Imperial and US customary measurement systems different concepts – the imperial gallon is defined in terms of the volume occupied by a specified mass of water, while the US gallon is specified in terms of cubic linear measure. Notes Notes Units of weight in both the imperial and US customary system always used the same standard, though differences in multiples of the avoirdupois pound developed in the nineteenth century. Both systems used the three different scales – the avoirdupois system for general use, the troy system for precious metals and the apothecaries system in the pharmacy industry. The term "weight" and "mass" are used interchangeably in
Gold IRA Savings Plan (TSP), and 401(k)s. The four precious metals allowed to be held in an individual retirement account are gold, silver, platinum and palladium, provided they are in the form of IRS-approved coin or bar products. Since gold is the most commonly purchased of the four, the overarching term "gold IRA" is used most often as industry slang to mean a retirement account containing any combination of precious metals. Other terms such as, "precious metals IRA", "silver IRA", "platinum IRA", or "palladium IRA" are also frequently used. Investors often use precious metals as a long-term hedge against inflation, to diversify