An article I wrote back in 2011 If your new to world coin collecting, and have wondered why some of the coinage from the 1600’s look to have a slight bend in them, and also be wondering why some of those coins bring high prices. Well, it was do to the design of the minting press and the dies used in the minting of those coins. Just visualize a flat piece of metal being pushed through two rolling pins that are going to be exerting a lot of pressure on that piece of metal. On these rolling pins are the dies used in the minting of the coinage. There were a few different types of roller die mint presses. One type used rollers that had dies all the way around it, and another type of roller press used a single obverse and reverse die on the rollers. Take a look at the pics of the rollers and dies used. pic 1) this is a roller die with dies all the way around the rollers. pic2) this is a milling press that would flatten out the strip of silver before be put into the minting press pic 3) this is a different type of roller die in which only one obverse die and one reverse die is used on the roller. pic 4) this is the minting press which used a single obv. and a single rev. die. Pic 5) this die shows how much of a bend a coin could have. Pic 6) click to make this pic bigger. This is a roller press If you would like to read part 2 just let me know.
The roller press was a major step towards the production of machine or milled coins. The mint at Segovia in Spain was the first to use this technology, in conjunction with the constant availability to power the presses, thanks to the centuries old Roman aqueduct. The dies initially used during the reign of Philip II were German engraved and of fine quality. Spain, Segovia, Philip II, 8 reales, 1590. Calico-167a 27.0 grams Perhaps the pinnacle of Spanish coinage is the 50 reales of Segovia, which must have required heavy duty mint presses to create the tremendous pressure to mint these massive coins. Spain, Segovia, Philip IV, 50 Reales, 1635 R. KM 81.5
