The first Lincoln cent was produced in 1909 and had the wheat ears pattern on the reverse side. The composition of the penny was pure copper from 1793 to 1837. Then following that, it was made of bronze, and in 1857, it was made out of copper. In 1943, the content of the coin was changed to zinc coated steel because of the copper shortage during World War II. Before 1982, pennies were 95% copper and 5% zinc. Then after 1982, the composition was 97.6% zinc, and 2.4% copper. So this means that the pennies made before 1982 will have a different mass from those made after 1982.
http://hypertextbook.com/facts/2002/MillicentOkereke.shtml
http://www.skyandtelescope.com/observing/home/Mercurys-Best-Show-of-2014-241696701.html
An old legend, almost certainly false, is that Copernicus never saw the planet Mercury. It's easy to see how the story took hold. Copernicus was mostly an indoor astronomer, wrestling with mathematics and generally using other astronomers' observations to work out his revolutionary model of the solar system. At his northerly latitude on the shore of the Baltic Sea, amid the local fogs and mists that he often complained about, the closest planet to the Sun may indeed have been an unusual sighting. Mercury's position in the twilights of late January.
Mercury is in fact the last bright planet that many sky-watchers identify. Mercury spends most of the time deep in the glow of sunset or sunrise. But now is different. Mercury has come out of hiding to put on perhaps its clearest show of the year for mid-northern viewers. It will be at its best from about January 24th to February 4th. It will appear highest on January 31st (if you're near 40° north latitude), more than 10° above the west-southwest horizon a half-hour after sunset and setting only as the sky grows fully dark.
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