Then tht's their own rule and is not required by the IRS regs. See below:
Investment in Collectibles If your traditional IRA invests in collectibles, the amount invested is considered distributed to you in the year invested. You may have to pay the 10% additional tax on early distributions, discussed later.
Collectibles. These include: Art works,
Alcoholic beverages, and
Certain other tangible personal property.
Exception. Your IRA can invest in one, one-half, one-quarter, or one-tenth ounce U.S. gold coins, or one-ounce silver coins minted by the Treasury Department. It can also invest in certain platinum coins and certain gold, silver, palladium, and platinum bullion.
Excess Contributions Generally, an excess contribution is the amount contributed to your traditional IRAs for the year that is more than the smaller of:
$3,000 ($3,500 if 50 or older), or
Your taxable compensation for the year.
The taxable compensation limit applies whether your contributions are deductible or nondeductible.
Contributions for the year you reach age 70� and any later year are also excess contributions.
An excess contribution could be the result of your contribution, your spouse's contribution, your employer's contribution, or an improper rollover contribution. If your employer makes contributions on your behalf to a SEP-IRA, see Publication 560.