Understanding the 90% Silver Standard
From 1792 until 1965, U.S. dimes, quarters, and half dollars were minted from an alloy of 90% silver and 10% copper. This composition was established by the Coinage Act of 1792 and remained consistent for over 170 years.
The 90% purity was intentional: the copper alloy provided durability for everyday circulation while maintaining substantial silver content. Pure silver coins would wear too quickly in commerce.
Today, this standardized composition makes valuation simple. Every dollar of pre-1965 face value contains exactly 0.715 troy ounces of pure silver, regardless of denomination. The NGC coin specifications database provides technical details on these coins.
Purity vs Silver Content
A common misconception is that higher purity means more value. In fact, investment value is determined by actual silver content, not purity percentage.
A 90% silver quarter containing 0.1788 oz of silver has the same silver value as 0.1788 oz of .999 fine silver. The purity percentage describes composition, not quantity.
This is important: 90% silver is priced by its silver content. The 10% copper does not add or subtract from the valuation since only the silver portion is valued.
Why the 90/10 Alloy Worked
The copper in the alloy served practical purposes: increased durability for handling, resistance to wear, and easier striking at the mint.
After decades of circulation, 90% silver coins show wear but retain their silver content. The copper wears before the silver, so silver content remains close to original specifications.
Purity and IRA Eligibility
IRS requirements for Precious Metals IRAs mandate minimum .999 fineness (99.9% pure) for silver. At 90% purity (0.900 fineness), pre-1965 U.S. coins do not qualify.
This is a significant difference between 90% silver and bullion coins. If IRA eligibility matters for your investment strategy, you must use .999 fine products.
For non-IRA holdings, the purity difference has no practical impact on value. Many investors hold 90% silver in taxable accounts and bullion in IRAs. For more on the historical significance of this alloy, see why pre-1965 U.S. silver coinage retains value.