For purposes of retirement plan investments, a collectible is defined as follows:
- any work of art,
- any rug or antique
- any metal or gem,
- any stamp or coin,
- any alcoholic beverage, or
- any other tangible personal property specified by the Secretary for purposes of this subsection
A retirement plan 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.
IRC § 408(m) , IRS Publication 590
Additional Helpful Information
Generally, any amount invested in a collectible is treated as a distribution from the plan for the year of the investment. The 10% early distribution penalty may apply to the amount.