Dear Mr. Berko: I’m interested in an advertisement by the U.S. Mint offering silver Krugerrands for $79.95. This is the first silver Krugerrand ever minted by the South African Mint for the U.S. Mint. Because it’s the first, do you think this will have value for collectors? And could you explain to me why a troy ounce of silver weighs more than a regular ounce of silver?
— C.P., Joilet, Ill.
Dear C.P.: As you said, a troy ounce, which is a unit of measure for weighing precious metals, is heavier than an avoirdupois ounce. But a troy pound is lighter than an avoirdupois pound. Confusing? Troy weight has been used for hundreds of years, named after Troyes, France, which is about 100 miles southeast of Paris. Troyes is a town of 60,000 people, with narrow cobblestone streets, colorful half-timbered homes and magnificent Gothic churches and cathedrals with striking stained-glass windows. Here’s how it buries.
Troy weight and avoirdupois weight have the same base unit, the grain. A troy ounce is 480 grains, or 31.1 grams, compared with the avoirdupois ounce, which is 437 grains, or 28.35 grams. The difference isn’t much, but things change when measuring large quantities of precious metals. That’s because there are only 12 troy ounces to a troy pound, whereas there are 16 avoirdupois ounces to an avoirdupois pound. Therefore, the troy pound is 5,760 grains, and the avoirdupois pound is 7,000 grains. That’s how an avoirdupois pound is heavier than a troy pound but a troy ounce is heavier than an avoirdupois ounce. And I thought calculus was tough!
Now, the U.S. Mint has nothing to do with the misleading advertisement you sent me from your paper. Frankly, some of our newspapers should do a better job of editing and policing the too-clever adverts that so easily fool the reader about costs and claims. Be mindful that truth requires facts but honesty requires full disclosure.
