I collect coins. I went to a big coin show last weekend, had a blast, but it reminded me that I've been neglecting my hobby for a while. So this weekend, I spent most of my unstructured time reading through nearly a year's worth of Coins magazine and Numismatic News weeklies that my grandfather'd given me. I also got some questions answered that had been bothering me by my lack of knowledge. For example, I now know what purpose a hub serves in the coin making process (although I couldn't tell you why it's called such a thing), and I understand how coins get an overstruck date (eg, 1918/7, "8 over 7"). Among the more interesting bits (at least, to a numismatist) I learned:
The life of a coin: an artist makes a plaster cast of the coin, about 12 times bigger than the real thing. The cast is in relief (ie, it's a "positive" image of the coin) and is used to create a galvano, also in relief. The galvano is put on one side of a Janvier transfer engraving machine, a blank hub of the size of the actual coin on the other, and the result is a relief impression of the coin on the hub. The hub gets pressed into steel to make a die, that's incuse (negative). The die is hardened, then can be used to strike planchets (blank disks of metal) to make the coins.
The date for a coin is not part of the hub -- otherwise, you'd need a new hub each year, and that'd be a pain. Instead, the date is stamped into the incuse design of the die. If the mint worker picked up the wrong die to make this stamp, the wrong date could be pressed in. Moreover, if a new die began service late in the year and hasn't been worn much, it's possible that it would be used for the next year by replacing the date.
There's actually a second layer of hubs and dies: the first are "master" hubs and dies, from which the working hubs and dies are created. The working ones will wear out over time.
The two-cent piece, first issued in 1864, is the first US coin to bear the motto "In God We Trust."
The US minted gold coins in values $1, $2.50, $3, $5, and some bigger. It also considered minting a $4 but these "Stellas" were never circulated.
The original US cent coin was a large cent, about the size of a quarter. In 1857 a new, smaller cent (same as present day diameter) was created. This being a time when the intrinsic values of coins was important to the public, the coin was a composition of copper and nickel.
Because of the US civil war, people hoarded their coins. Gold and silver coins had instrinsic value. Surprisingly, people also hoarded their copper/nickel cents, whose value was really only about half a cent. The Mint Director lobbied Congress to authorize a new bronze composition for one and two cent coins, but a powerful nickel mine owner lobbied against. The debate contined until 1864, when Congress finally authorized bronze for the one cent coins, and for the creation of the two-cent coins.
The small motto 1864 variety was never supposed to be circulated, it was much more of a pattern coin.