In minting, coining or coinage is the process of manufacturing coins using a kind of stamping which is now generically known in metalworking as "coining". This process is different from cast coinage, and can be classified in hammered coinage or hammering and milled coinage or milling.
A coin die is one of the two metallic pieces that are used to strike a coin, one per each side of the coin. A die contains an inverse version of the image to be struck on the coin. Striking a coin refers to pressing an image into the blank metal disc, or planchet, and is a term descended from the days when the dies were struck with hammers to deform the metal into the image of the dies. Modern dies made out of hardened steel are capable of producing many hundreds of thousands of coins before they are retired and defaced
Prior to the modern era, coin dies were manufactured individually by hand by artisans known as engravers. In demanding times, such as the crisis of the Roman Empire in the 3rd century, dies were still used even when they became very worn or even when they cracked. The die that was on the hammer side, usually the reverse (back), tended to wear out first. The planchets were usually hot prior to striking. On some Roman provincial coins, some believe the tongs used to move the heated planchet left permanent center indentations on the finished coins. Others attribute these marks to surfacing tools used as a part of planchet preparation. Experimental archeology suggests that a lower die could be expected to last for up to 10,000 strikes depending on the level of wear deemed acceptable. Upper dies seem to have a far greater range of lives with usable lives ranging from just over 100 strikes to nearly 8000 being reported. Combining archaeological evidence with historic records suggests ancient coin producers (in this case the Amphictions at Delphi) could get as many as 47,000 strikes out of an individual die.
Medieval engravers were guild members who created coins. The vast majority of medieval coins were cold struck; the planchets were not heated. While medieval coin dies were largely made of iron, some dies have been discovered with a small region at the face of the die which is made of steel. As technology and the economy changed over the course of the Middle Ages, so did the techniques used to create coin dies. While most ancient coin dies used engraving very heavily, early medieval coinage was dominated by dies created mostly from punches, which displace the metal of the die instead of removing it. There is evidence of medieval die cutters using engraving tools to lay out designs and to create detailed punches. However, engraving on the face of the die did not become commonplace until the early Renaissance.
Very detailed records exist for the Venetian mint. In the late Middle Ages, the dies used to create tornesellos lasted as follows: "hammer" die, ~17,000 strikes; "anvil" die, 36,000 strikes. The mint made an average of 20,000 coins per day, so they were making one hammer die a day and one anvil die every other day. The "hammer" dies wore out more quickly because they tended to be smaller and were hit directly with a hammer, leading to severe mushrooming on the tops.
Mintage numbers are something that coin collectors must become well-versed in if they are to understand part of what makes a coin valuable, as well as what helps to make a coin rare.
The mintage number of a coin simply refers to how many coins were struck by the mint. It does not, however, necessarily refer to how many coins still exist. After all, there are many coins which, over the years, have been minted in great quantity only to be later melted down or destroyed, either by the mint or by private interests. There are also many coins which have inevitably become lost to time, either through burial or corrosion. There are also countless coins which have been lost through disposal, which can happen unintentionally or purposefully, therefore, a mintage number essentially acts as a means to help one understand how many coins the mint actually made, it in no way solidly tells us how many coins of a given date or mint mark may actually be left, though there are many people who have estimated such numbers.
As you may imagine, to know what a coin’s mintage number is can be very important (even vital) to understanding how rare coin is, after all if we are to judge the issue of supply and demand, we must know how much supply there is (or at least once was) to get a better idea as to how significant relative demand really is for a coin.
Many silver and gold coins with seemingly high mintages actually may be far scarcer than a mintage number would indicate, that is because during times when silver and gold have become particularly expensive (such as during the late 1970s and early 1980s), people have actually sold these coins by the millions to scrap metal dealers who place the coins in the melting pot.
If you understand the idea of supply and demand, you will quickly see how the aforementioned pricing scenario is not really odd at all. In fact, it makes perfect sense. After all, there are relatively few collectors who take time to acquire Bust dimes, and many of those who pursue Bust dimes do not even attempt collecting a whole run of dates, therefore, demand for the 1837 Bust dime is far lower than that of the 1909-S V.D.B. cent (a coin often dubbed one of the most sought-after rare coins). Consider that the 1909-S V.D.B. is a coin which belongs to a very popular series of coins (Lincoln cents), furthermore, Lincoln cents are usually collected as a series, which means one must have the 1909-S V.D.B. cent in order to complete a collection of Lincoln cents. This phenomenon has made a number of 20th century silver and gold coins far more scarce than mintage numbers may suggest.