I would like to remind you of this thread (about the curious 1769 5 kopeeks):

http://www.coinpeople.com/index.php?showto...18720&st=40

I have a very vague notion of the technology used in that era, so that discussion was both interesting and somewhat educational for me. As a result I think I started paying more attention to the possibility of such defect. I must say that in the short time that passed I have seen a surprising number of these error coins (randomly, just on eBay). I can now understand why Rittenhouse liked that coin so much. Most of the examples I've seen so far have much shallower imprints. I bought a couple of such coins, and I would like to present them here. I am still somewhat confused about this subject.

Here is my new 1769 EM 5 kopeeks (another one). Same year, same mintmark definitely a different set of dies (this one is an overdate). On the averse (part with the date) you can see an imprint of the wing, the cross and sphere, and a part of the banner that holds the "piat' kopeek" inscription. On the reverse there is a faint imprint of the laurus (?) branch, and a berry.





Here's another example of a coin with dual (both sides) imprints, this time not mine:





However, if you recall my original 1769 5 kopeeks had imprint only on one side. I recently bought this 1813 EM 2 kopeeks with a very similar defect (single sided):





I have also seen this coin - 1791 EM 5 kopeeks, also with an imprint on a singel side of the coin (this time on the eagle):





I have seen a few more coins with minor imprints, all appear to be from Ekaterinburg.

So my queries are - Are all of these a result of die clashes? Why are certain coins defective only on one side? Would it be possible for the mint workers to have simply filed off the damage from a die? Does anyone have any kind of a guesstimate on how common such coins are?

I think so.



My guess is that the dies might not have worn out at the same time. Maybe a pair of clashed dies might only have had one die replaced with a new one while the other continued in service.



They seem to show up with a certain regularity, possibly more common on certain dates & denominations than others. I have an 1841 5 roubles which shows heavy die clashing on both sides. Other examples of this coin that I have seen offered also show this same clashing and appear to be from the same die pair.

I am definately challenged - I really doubt clashed dies can have that much clear impact on the opposite side of the die. I am still thinking that it's more likely that there must have been several brokeage coins struck which was then "fixed" by striking the problem side.

This is true but there is another possibility. Sometimes damaged dies were taken out of the press
and ground down to remove clash marks or other defects. This refinished die was then put back
into the press for further use.

RWJ

Thank you. I was aware of die polishing but not aware of the practice you describe.

If you have a photo in your database which shows an example of a coin struck from a die which has been ground down in the manner described, I ask that you please post it. I am very interested to see one. Thanks!

Yes, they are all clashes. A brockage looks much different. A "typical" single-side brockage will show one side with a normal raised strike and the other and a rather mushy incuse impression of the same side. This is caused by a coin becoming stuck to one die. When the new planchet is fed it is struck between the one die and the stuck coin. Just google brockage and you'll see examples. Given the size of the 5K I rather doubt that a brockage is possible.

As RWJ notes, one cause of single-sided clashes is that the other die was replaced. The original die was either so damged it was discarded or it was removed for repair by lapping (polishing with a zinc or brass lap and fine polishing compound).

Another possible cause is the dies themselves. The steel at this time was not uniform. One die could have been significantly harder than the other resulting in clash damage to one but not the other.

Thanks everyone! Once again your replies are informative and eye opening. I did make an assumption that the mint workers would polish off the damage from the dies when they saw the defective coins, but more likely they just let them run. So that would explain the relatively high quantity of these coins that I saw pop up over the last 2 months.

I’ve noticed a few coincidences.

First, so far all the coins that I’ve seen came from Ekaterinburg. I haven’t seen enough material to claim that other mints did not have this problem, and it could be because the EM mint was very busy throughout these years. But is there any difference in the way that mint was run that can explain the overall lower quality of their production?

Second, more specifically to the 1769 5 kopeeks. Is it a pure coincidence that the both coins are struck stronger on the left side (relative to the averse), hence the die damage? Or is it in someway particular to the equipment of that period?

I also noticed something curious on the new 5 kopeeks. The incuse imprint from the banner lies right on top of a berry on the averse. However, on the flip side the berry left an imprint on the die above the banner, so the dies have shifted positions sometime between the clash and the sticking of that coin. Like I said, my understanding of the machinery is vague, so perhaps dies could shift after every strike.

This was a general practice at world mints as it saved time and effort in preparing a
new die. I do not have any illustrations for Russian dies but those for U.S. exist if
memory serves correctly. Rittenhouse can probably furnish examples.

RWJ

Very interesting. Thank you for this information.

I am somewhat surprised by the use of the lapping process. Was this used on copper?

The reason I ask is that the 1841 5 roubles I mentioned shows heavy clashing and I always thought that the gold coins were typically struck with greater care than the silver or copper coins. So, why would lapping be used for copper while (at least, in the case of the 1841 gold coin) the dies remained in use despite the damage?