Siberia 10 kopeks 1769KM triple struck - but how?

[sigistenz]

 

Something went wrong but I cannot imagine how this happened . The two jaws of the screw press holding a die each should meet centered. Thus the 3 strikes

should show similarly on both sides - or was the screw press falling apart? Can anybody explain why the nominal side does not show likewise 3 impressions?

Thank you for your consideration and reflections,  Sigi

[extant4cell]

The only thing I can come up with is that the cipher side's die was badly fixed and with every turn of a screw it moved further and further away from it's usual central location leaving moving image imprints. May be there are other explanations?

[IgorS]

Interesting defect.

Here is a demo on how the screw press operated:

 

 

[extant4cell]

Very interesting video.

I think this one would be good for small coins only though. There is a somewhat similar hand operated machine described by Nartov in 1779 for small gold coins production on SPM:

 

Large copper coins required a lot more pressure.

Spiranski described large copper coin production on EM and the presses that were used there in 1780 (and probably way before that). As technologically KM was a subsidiary mint to EM, their presses were similar to the ones on EM. Presses operated with the help of water power and 2 leather belts (one to move the press screw down, for striking and another one to move it back, parting the dies). I think, if the coin would get stuck to one of the dies, the quickest way to release it was to strike again.

Both dies (top and bottom) were held in their positions with 4 fixing screws each. I believe, if not properly fixed, one of the dies could move.

In my digital library there a few publications on coin production, but when it comes to EM/KM large coppers, Spiranski is the best to rely on.

Details on EM 5 kopecks presses are on page 13 and 14 in Spiranski.

Spiranski - 1907

Description of Ekaterinburg Mint Production in 1780 1907 (3Mb)

Additional materials (in Russian and German [Schlosser - 1884]):

Nartov - 1779

Desctription of Monetary Production
courtesy of Mr. V. Arefiev

 

Vollendorf - 1883

Condition of coin minting
courtesy of Mr. V. Arefiev

Schlosser - 1884

Technique of Coins and Medals Production
courtesy of Mr. V. Arefiev

 

[sigistenz]

Thank you for the demonstration and explanation of the screw press,  there is always something new (or long forgotten, coming back to mind).

It is indeed quite likely that the 3 differently placed  die impressions on the cipher side are due to a loosening and slipping upper die.  Before the operator  realized    and could switch off power the press struck a second and a third time. The 3 strikes  flattened and widened the coin to an enormous diameter of 51mm (instead of the normal 45).  See the compression on both rims of the edge.

Sigi

[IgorS]

22 hours ago, extant4cell said:

Very interesting video.

I think this one would be good for small coins only though. 

 

 

Yes, in deed. I also find the video interesting. It shows screw press at work. When one sees a picture of a screw press, it is hard to imagine how fast it operates. The video certainly gives it a better visual representation.

[extant4cell]

It was a good question, and interesting to look through the publications again. Seeing press in action was a nice bonus too!