Hey Coop or whoever chooses to answer...I watched the video for the double dies that Coop has listed in his signature area. I have just a few questions regarding a double die...first of all how does this happen? Does a coin get struck more than once while it is being made...because a lot of the double dies I see are in the words/(devices as you all call them) but not on the bust of the coin which would indicate that the words/devices are struck seperately from the rest of the coin. The definition of double die in its own wording would mean to me the coin is struck twice or more...or does the die itself got the doubling already in it that creates the problem. Why is there only doubling on one side of the coin as opposed to both sides of the coin most of the time...are the obverse and reverse struck separately? Is there a video anywhere that shows the coin making process?
A doubled die occurs during the hubbing process (where the design is put onto the dies) when the design is inadvertently duplicated on the die. Therefore the die has the doubling and every coin struck from that die should in turn also show the doubling.
The are multiple "classes" of doubled dies that explain the different ways in which the design can be duplicated in this process. US doubled dies are also divided into two eras: multiple-squeeze (before 1996/7) and single-squeeze (1996/7 and on). This is because the mint changed their hubbing process from one where multiple squeezes or presses were needed to fully hub the design into the die to another where only one squeeze is needed. Doubled dies have a different appearance depending on which era as each have different possible classes.