United States customary units mass: tower, apothecaries', troy, avoirdupois, and metric. Of these, the avoirdupois weight is the most common system used in the U.S., although Troy weight is still used to weigh precious metals. Apothecaries weight—once used by pharmacies—has been largely replaced by metric measurements. Tower weight fell out of use in England (due to legal prohibition in 1527) centuries ago, and was never used in the U.S. The imperial system, which is still used for some measures in the United Kingdom and other Commonwealth countries, is based on avoirdupois, with variations from U.S. customary units larger than a pound. The pound avoirdupois,
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