This is not for those who refuse to question. It's not for those who dont look deeper into meaning. It's not for those who say, "it is because, it's always been and I say it". Lol When a die has an engraving error WHY would people expect it to ALWAYS be equivalent to the intended, in regard to depth and quality? I mean their could be incomplete engraving error types of die doubling that effect the die? Ok. What I'm referring to is the double dies that must be part of the die, not part of the process. Therefore, double dies are uniform varieties, which collectors seek. This is not disputed. However, it is known that some double die varieties also have die clashes, or other defects, that make their classification a bit dubious. On the other hand, its noted that some machine doubling closely mirrors a double die. I'm going to show a real life example, and I've seen many others. This example shows what's currently known as "machine doubling" on the date, face, and eyelid. HOWEVER, it is NOT in a uniform direction. It is also not physically possible to be involved in a "pivot". ...the doubling doesn't line up correctly. Another thing is that, although doubling of the numbers may be flat, and shelf-life, there appears to be a clear sherif on the tip of the 9. Also, many other "machine doubles" examples show "shelf-like" appearance but the tips or ends of the numbers are equally raised. Perhaps? Some "machine doubling" is part of the die engraving process. Anyone who has done engraving by hand can tell you that the initial process is the most difficult. Once the groove starts it becomes easier. This is not done by hand BUT vibrations could cause a wider grove initially. This would transfer a "shelf- like" appearance in some areas, while other areas appear to be "true" doubling, like the eyelid, series, and raised number ends...? This is a peculiar aspect of "machine doubling". Perhaps a loose die during engraving or other similar explanations, related to the process of "double die"?
First, I should point out that working dies are not engraved. The only engraving that takes place in today's modern method of making coins comes when the design on the Galvano is transferred to the master hub by way of the reducing lathe. From then on, the design on the master hub is pressed into the master die which is then pressed into the working hub which is then pressed into the working die. Regarding machine doubling, there is no way that anyone can predict which part of the devices may be affected by the vibrations from a loose die that is rattling back and forth at blinding speed. Chris
From your original post: This is not for those who refuse to question. It's not for those who dont look deeper into meaning. It's not for those who say, "it is because, it's always been and I say it". Lol Mechanical doubling is not some arbitrary definition that some numismatists came up with while having cocktails at an ANA convention 100 years ago. It is based on the understanding of the mechanical and physical processes during minting. Based on your post, it appears that you still need to learn a little more about on the die making process. Remember, you have a master hub, that is used to make a master die, that is used to make working hubs, that are used to make working dies. No hand engraving. Also, don’t assume that the die movement causing mechanical doubling is only rotational. It can move in a number of directions depending on what part of the equipment/fixturing is worn or loose. The following should help increase your understanding: https://varietyerrors.com/coin-dies-made-little-history/ http://www.coinnews.net/2013/09/13/how-the-philadelphia-mint-makes-hubs-and-dies-to-produce-coins/ The Mint also has some videos on You tube. I haven’t watched them, but am assuming that videos from the USMint.gov aren’t likely to be clickbait. (looks like Chris just said the same thing in his response)
I guess you and I must fall into one of these categories. No, wait! There is one more! "It's not for those who know the correct answer." Chris
I have given thought to the idea that a form of mechanical doubling could occur during squeezing of a working hub. Producing characteristics that emulate strike doubling such as design devices exhibiting shearing with a flat shelf like appearance which would transfer to a working die.
It's not for those who understand the minting process. MD happens, you can't explain it as so many working parts wear and that causes them to become loose. Add in zinc planchets and it becomes worse. That's the way it is so accept it.
Some of the discrepancy in where on the coin MD occurs can be explained by height differences between the devices. Take a look at this 1957-D with strong MD on the date, yet not a hint on the MM. Looking at the coin in 2-D, it is difficult to explain why this would happen, but the 3-D / perspective shots show that the MM has lower relief than the date. The MD damage caused significant damage to the date, yet is shallow enough that didn't touch the MM. http://www.macrocoins.com/1957d-mdd.html
O Look familiar here’s my really nice example of machine doubling and that is all it is simple machine doubling! Reed.
For coins before the advent of single squeeze hubbing, the mintmark was added after the completion of the hubbing as most dies were made in Philadelphia and shipped to the Denver and San Francisco mint where the mm was added before use. Since it was by hand the force applied by the workers hammer decided its depth in the die and thus its height in the finished coin, so although the difference is usually too small to measure, it is realistic that some difference in height on the coin is to be expected. Single squeeze coins as I see explained, the mm is added in the computer engraving of the master die , all at the same time. When looking for varieties such as DD or RPMs, one MUST know if they are single squeeze ( usually after 1995) although a little experimentation was done earlier, or the older classic and true DD before. Too many people are trying to identify DD and RPM on single squeeze coins by the characteristics of the older multi-squeeze coins and rpms similarly. IMO Jim
Looking at the 3-D images provided by rmpsrpms - it appears the mint mark was punched into the die at a tilted bias towards the lower west side of the "D". Which when in reference to an actual die would be to the lower east side of the "D". This indicates to me the engraver held the punch with his left hand and stuck the punch with a mallet held in the right hand. This is assuming of course that the engraver positioned the die up right when punching the mint mark into the die.
