I specialize in overdates, and have assembled a poster of images that show a few of the most common diagnostics for overdates. In other words, where are you most likely to see the "7" poking out from beneath an "8"? This poster shows some of the most likely date combination--many more exist. With a couple of exceptions, these are all in my collection.
Nice poster! I have a question. Is the number that is an overdate always the next number in its sequence? so 2 over 1, 3 over 2, 4 over 3 etc.. I should know this but I don't So can there be an 4 over 2 or an 8 over 6?
Thanks! Yes--an overdate just means a die from a previous year was reused and the new date added--it can be any combination of numbers, such as my profile pic: 9/4. And, sometimes there can even be several dates impressed in the die, such as 1965/4/3--I hope to get that one soon!
Before they directly engraved the date on the dies, but used a device where number punches ( forget the name of the device) were aligned by hand and used to punch the dies, like some of the half cent and cent, and higher values, error were made such as 1824/22 large cent, large 1820/small 181, and even a very popular 1828/88 large cent, and others. Once the date was engraved directly, such large disparities became less. But I agree with Kurt that their intent was to only go up one year.
The handwork evident on mid-1800s US coins is really interesting--and it's similar on many European coins from the period. Overall, it depends a lot on mint practices which part of the date was on the hub and transferred to the dies. Sweden went to a full date hubbed into the dies after 1916; at least I haven't seen any overdates or repunched dates later. Norway kept the practice of adding the last two digits to the dies into the late 50s, perhaps even into the early 60s. I base this on studying old hubs at Norway's Kongsberg mint. Canada was adding the last two digits on some dies into the 50s. In the US, dating dies individually ended around 1909. Of course, the concept of overdates gets more complicated when some mints re-dated their dies by using a newer hub. Such is the case for US overdates after 1909, like the spectacular 1942/1941-P 10c, the 1918/7-D nickel, or the 1918/7-S quarter--I'm still looking for those (unattributed)
Just as some more info, the overdates pictured above are from Mexico, Sweden, Belgium, Australia, Norway, USA, and Peru.
