Precious Metal Weights and Measures

Because the value of a Franklin Mint set depends largely on its precious metal content, it's important to understand the terminology and units used for measuring gold and silver, and how to use this to determine the bullion value.

Precious metals (gold, silver, and platinum) are measured in units called troy ounces. When you see in the newspaper or the Internet (e.g., at the bottom of this page) that the spot price of silver is, for example, $25, this means that the going price for 1 troy ounce of pure .999 silver bullion, as a commodity, in large quantities, is currently $25. A troy ounce is not the same as the commonly used ounce weight - an avoirdupois ounce - which is what you get if you weigh a medal on a postal scale, although they are close (about 10% difference). Both types of ounces can be measured in terms of smaller units called grams or grains.

1 troy ounce = 31.103 grams = 480 grains = 1.097 avoirdupois ounce

1 avoirdupois ounce = 28.35 grams = 437.5 grains = 0.911 troy ounce

Where you have ounces, you also have pounds, and this gets even more confusing.

1 troy pound = 12 troy ounces

1 avoirdupois pound = 16 avoirdupois ounces

Throughout this site, when the term "ounce" or the abbreviation "oz" is used, it should be understood to mean troy ounce.

Purity

The purity of metals is measured in terms of a percentage or fraction of 100% pure. Because no refining process is absolutely perfect, 100% purity is not technologically achievable. Normally .999 or 99.9% is considered as "pure" silver or gold. Modern refining processes can achieve .9999 or better purity, but this is more costly and largely a marketing issue (for example, the American Buffalo is advertised as the U.S. Mint's first .9999 pure gold bullion coin). Gold purity is also expressed in terms of "Karat", abbreviated K or sometimes KT, where 24-Karat is pure gold.

Most Franklin Mint silver issues are minted in Sterling Silver, which is 92.5% or .925 pure silver, although a few are .999 silver. Solid gold or platinum Franklin Mint issues are exceedingly rare, but most are .999 pure. Other private mints, e.g., Danbury Mint, have issued 14KT gold medal sets.

Common Franklin Mint Weights

Common weights for Franklin Mint issues are 500 grains (1.04 troy Ounces) and 1000 grains (2.08 troy ounces), although sizes of 300, 600, 750, and 900 grains were also made. Larger items were made mostly in 1500, 2500, and 5000 grain sizes. The Franklin Mint did not make any even ounce size items (e.g., 1.0 troy ounce and so marked) that I am aware of, although other private mints commonly made the 1 troy ounce size.

Determining Bullion Value

Putting this all together, you can determine the bullion value of a Franklin Mint set by calculating (weight * purity * price). For example, for a set of 50 500 grain sterling silver medals, with spot silver at $25/oz, the calculation is:

50 pieces * 500 grains = 25,000 grains

25000 grains / 480 grains per troy ounce = 52.08 troy ounces sterling

52.08 troy ounces * .925 purity = 48.12 troy ounces equivalent pure silver bullion

48.12 troy ounces * $25 spot price/oz = $1203 actual bullion value

As an easy guideline, the 500 grain sterling silver size is about .96 oz. pure silver, and the 1000 grain size is about 1.93 oz. These are commonly thought of as 1 oz. and 2 oz. pieces.

Gold Plating

Because gold is so valuable, many people wonder whether the gold plating on Franklin Mint medals contains a significant amount of gold that would make them more valuable. The answer is no, because the gold plating is so extremely thin that there is a negligible amount of actual gold in the "24kt gold electroplate". Most gold plating is about 10-20 microns thick (1 micron = .001 millimeter). For comparison, a dollar bill is about 200 microns thick, so we're talking less than 1/10 the thickness of a dollar bill! The gold-plated silver medals look great, but the value is the same as the silver value.