Is there a way to tell if a coin was rolled rather than pressed? The coin will have a slight bend (thick pieces) or wavy look to it (thin pieces) depending on the thickness of the strip of metal. How widespread was the usage of this type of machine? By 1585 there were 13 known mints using this type of minting. Mints were in use in Germany, England, France, Austria, Slovakia, Romania, Switzerland and Poland. There were smaller mints also during this time. I guess you could them branch mints, as these mints had to get the ok by the Emperor to mint coinage. Oh, and these were strips rolled through at one long run, right? I wonder how they were then cut and separated? There were trimming or punch machines. (I’ve included a pic of a punch press) The mint master would use shears to trim off any metal that trimming machines or punch press may not of remove. Also of note. When the mint warden would weigh the coins, if any coin was over weight, a file would be used to bring the weight of what the coin should be. When you see a coin with these file marks, it is call adjustment marks. It was a very common practice at that time. The process reminds me of the elongated penny machines that are still used. But when one is run through, it's...well, elongated. I wonder how this is avoided. Less pressure maybe? The metal strip being used was flatten out to different thicknesses depending on what the coin was to weigh. These strips were also flatten out using a roller press. More pressure, the thinner the strip. The process would take a while as the pressure on the rollers had to be changed many times to get the strip to the thickness it needed to be. After the thickness of the strip was set, the hardest part in the minting process was over. All that needed to be done for the die press, was the set enough pressure to mint the blank. Pic #1 is of a puch press used to punch the coin out of the strip.
Yes, roller die produced coins are often times a bit wavey and sometimes a bit oblong. Also, my under standing is that the coins were cut with shears from the strips of silver. These must have been formidable shears, definitely not for sewing! After the cutting the edges must have been smoothed somehow. Here's a Leopold I thaler that is somewhat not level, what one would expect from a screw press. There's a warp in the flan in the center of the coin. It also has the characteristic oval shape. Holy Roman Empire, Leopold I, thaler, 1691, Hall. KM 1349 28.41 grams
The mint master would use shears to trim off whatever needed to be after the coin left the punch press. Nice coin you have there.
While I don't doubt that overweight coins from roller presses had their edges filed I believe the term "adjustment marks" typically refers to those made on the surfaces of the blanks prior to being struck with a screw press. The proper weight of a coin from a roller press could only be measured after it was struck and subsequently stamped from the strip and you wouldn't run a file over the surface at that point. But you could measure a blank stamped from a strip for proper weight prior to being struck in a screw press. In this case, you would avoid filing the edge so that the edging mill could impress a full design and the impact from the screw press would normally obliterate the file marks across the blanks' surface. The mill that flattens the strip can also leave parallel grooves on a strip so you might see such marks on weakly struck coins from both roller and screw presses but these wouldn't be considered adjustment marks.
One thing that new collectors have problems with, is how to tell the difference between die polishing lines and surface scratch's. The book I'm working on will have photos and explanations on how to tell the differences between the two.
That would be very helpful. Some of the die polishing lines are quite obvious, while finer polishing lines require magnification, sometimes quite high. Die polishing lines result in raised ridge-like lines and appear in the fields, often extending into a coin's legends. Also, if the coin is high grade and there's still mint luster present, it will cover the die polishing lines as well as the devices and letters. That's been my experience.
I've seen some that almost look like elongated coins! The core of my German States collection lies at the height of roller press minting (much of the 17th and 18th centuries). From my experience, minor coins from Augsburg and Nurnberg often are very "taco" shaped from the process which really makes them hard to photograph! When coins are off-center by even a couple millimeters it is very easy to ascertain they were roller milled because the planchet is all there, but the design (including denticles) is partially missing. These coins are often mispunched out and they end up looking clipped ( I've seen this a lot on Livonian coins). A few roller milled coins. These two show the misalignment with denticles. Saxe-Weimar-Eisenach Bremen These show, hopefully, very curved planchets. Especially on the obverse of the coins, you can see how the light shifts from bright to dark simply because of how curved the coin is! My favorite roller milled beauty, a little half kreuzer. Because of the old holder, it's difficult to tell, but it is extremely curved!
