Today's the anniversary of the start of our pennies project, in which we're sifting through all the cents that were brought home every day by our reader Ben for more than 20 years. Lately we've been cranking back up on the project after a period of inactivity. We'd been sorting through the coins in chronological order -- the oldest was from 1929 -- and when we got 1982, things got complicated.

In 1982, the U.S. Mint changed the metal composition in the penny, from mostly copper to mostly zinc. But the Mint did this in mid-year, and so some of the 1982 pennies are made mostly of copper and the rest mostly of zinc. If you're being a thorough collector, you must treat the two types as separate, and since they look identical, the only way to tell the difference is by weight. The copper ones are a little heavier than the zinc ones -- about 3.11 grams instead of 2.5 grams.

Some folks say they can tell the difference by the way the pennies sound when dropped on a hard surface. We tried that a few times, to no avail. And so it was off in search of a scale sensitive enough to differentiate a 3.11-gram object from a 2.5-gram one.

We put out a call on this blog, and of course, there were a couple of readers who came through with an offer of a scale that would do the job. (One of the real beauties of this blog is our ability to ask for favors from knowledgeable people, and enjoy the generous response we invariably get.) One reader, Leigh, has a scale that he sometimes uses to measure out gunpowder for packing into rifle cartridges. He's a firearms instructor, and a steady hand when it comes to gun matters. In contrast, we don't know a thing about bullets except to stay away from them.

But anyway, after putting the loan of the scale on both of our long to-do lists, and while the holidays came and went, it took a while for us to show up at his place and pick it up. But we're glad we did, as it turns out to be just the ticket for a task such as this. The darn thing is sensitive down to a measure known as a grain, which is a teeny weeny fraction of a gram. 3.11 grams is the equivalent of 47.9945 grains; 2.5 grams is 38.5808 grains.

Leigh showed us how the thing works, and we packed it back to our place to start a-weighin'. The best technique was to set the scale at the weight of the lighter zinc penny, and see what reaction it gave when a penny of unknown composition was placed on it. The copper ones pinned the scale easily; with the the zinc ones, the pointer floated up and down before settling somewhere near the center point for the mark we set.

We don't have an exact tally yet, but there were about an equal amount of copper and zinc pennies in the 1982's. We've got them separated now, and can resume cataloging them. Logjam broken!

But first -- we had another wicked idea. We read on the intertubes somewhere that sometimes the Mint mistakenly uses old metal stocks in making new coins following a change in their official composition. Wouldn't it be something if one of Ben's 1983 pennies was actually made of copper? Now, that would be a valuable find. And so more weighing was in order.

An important side note should be made at this point: One thing of which this project has reminded us is that the Mrs. is highly tolerant of our many idiosyncracies.

In any event, we've got almost all the '83s checked now, and so far there's no copper penny in there. And so it will back to the mundane sorting, inspecting, and chronicling of what is in there. Ben will likely wind up keeping all the copper pennies, because their metal content is worth more than one cent. And if we find a rarity in the later years, we'll all have a party. But run-of-the-mill cents from 1983 and later -- like the 1982 zincs -- will probably wind up heading to a bank in exchange for something better. A credit to a checking account with an associated debit card sounds good.