Anyone see this 2000 sac rpm before?

JRocco

This looks like a strong RPM on a 200P Sac. I don't understand this- isn't it really unlikely to see an RPM these days? Nothing else is doubled at all on the obverse so it doesn't look like MD- what gives???

dlimb2

Looks like a good one to me...I think the Mint is trying to play games with us..yeah, sure right the single squeeze.

coppercoins

It's machine doubling, which is rather common. One tell-tale sign is that the existing "primary" mintmark is too thin, and the base of the doubling plus the primary mintmark are the right size and shape for ONE normal mintmark...which means this is a normal mintmark, part of which has been scooped to one side... machine doubling.

And yes, all Sacagawea dollar dies are created with a single squeeze...which would also have nothing to do with RPMs.

coppercoins

Of course the other telling sign is that mintmarks have not been punched into dies at all since 1989 - so RPMs cannot exist by nature on post-1989 coins. They are on the original engraving that turns in the janvier lathe to create the master hubs. So unless the original engraving has a doubled mintmark, nothing but machine doubling could cause a doubled mintmark...and if the original engraving had a doubled mintmark, then ALL the coins would show the same doubling.

anoldgoat

I've seen this as always expained as machine doubling. What has never been answered is how can one character/number show machine doubling when the characters/numbers next to it show none at all. I have a 1977 nickel with what looks like obvious machine doubling on the first 7 while the 9 and 7 on either side show none.

Anyone?

Please

JRocco

Thanks for the reply C.D., now I know what it is. It did look shelf like, but I was surprised that there was no other doubling visible anywhere else.

coppercoins

I know specifically how to tell the difference and can do it without a problem - but get into the dynamics of what can happen with a piece of metal in a retaining collar being struck with 40,000 pounds of force in less than a second then moved off to a bin for another piece of metal and another strike in less than a second, and the whole world blurs for me.

This would take specific knowledge of the machinery, the settings on the machinery, knowledge of how the dies are set into place, exactly where the keys are and how the dies are screwed into position, the hardness of the metal in the dies and planchets, and a really good knowledge of how those two metals work together.

All I do is study the results...it's either a doubled die or machine doubling. Put them in two boxes and I'm okay with that and reasonably accurate.

coppercoins

On a final note, there ARE INDEED doubled dies on single squeeze coins - so don't stop hunting.

mrpaseo

Don't forget metal flow...This phrase alone is amazing to me

Cam40

I thought a true DD involved the working dies themselves and had nothing to do with
striking techniques.
For a coin to be struck once, remain in the chamber and is struck again only slightly out of line
from the previous striking may be a doubled strike but not a `doubled die` strike.
It would technically be a machine doubling or strike doubling.
Can these two phenomenon be distinguised from one another just by examination?

Maybe they would look identical despite the different methods of achieving the end result?

coppercoins

Cam - If your post was in response to one of mine, I'm afraid you may have misunderstood my babbling. The strike, move, strike, move, in under a second was a reference to how fast the press strikes and moves coins out of the way for another to fill the chamber. As far as I know none of the modern business strike coins are purposefully struck more than once.

Secondly, there are different forms of machine doubling and they are distinguishable. Those that happened in a single strike are readily different from those that happened as a result of multiple strikes. The single struck coins have a "scooped" appearance as does Jrocco's mintmark. The multiple struck coins actually flatten parts of the devices on the second strike and show any imperfections in the fields on that second strike. The bits of the devices flattened during the second strike are usually much more flattened than the single struck machine doubled coins with the "stair-step" doubling. None of these have much if any following by a market so they aren't widely studied or cared about.

Cam40

anoldgoat- my theory on why one character shows doubling while the one next to it doesnt
is the doubled one is showing the deterioration of the die in that area of the die.
That tiny edge becomes worn and metal flow isnt dispersed normally. So it shows up
on the coin as some kind of weird doubling.

Cam40

C- Yes I understand. That is evident in the striking of that weird Jeff struck on a Cent planchet.
Did you see that thing? I think the guys at the Philly Mint got bored one day and we,re just seeing the evidence of that with that coin.
JMO

coppercoins

I don't think I saw what you're talking about, but I rarely pay a lot of attention to errors. They are nice to look at, but go pretty much in one ear and out the other for me. I don't remember them.

Cam40

Nickel in question:





E-Bay link

richbeat

Machine doubling on circulating coins most commonly occurs when one of the dies becomes loose. When the planchet is struck (once) by the loose die, it will shift slightly and cause shearing of various parts of the design. I've also heard this referred to as "die chatter," and has nothing to do with how many times the planchet is struck, as circulating coins are only struck once. Tightening the die usually fixes the problem. As a rule that shift, or shear, is what gives machine doubling its shelflike appearance. Mint marks commonly show machine doubling while the rest of the coin looks normal. The deepest part of the die will be affected by machine doubling first, and that is often the mint mark and that is especially true of the mint marks that were hand punched. I would think that the degree of the looseness of a die would have an effect on how much machine doubling there is, whether it's one or more letters or numerals, mint mark, etc. Coppercoins made a good point--there are many factors that come into play.

richbeat

Not to confuse anyone, but I am referring specifically to coins (planchets) that are struck once. See coppercoins post above.

coppercoins

Cam - That coin is rather a rarity because the coin has to be struck, flip over in the chamber, the get struck again. It's a flip-over double struck.

Cam40

C- I thought the coin was a culmination of boredom and alittle extra time on the hands of a few
Mint employees.
But, what do I know.....lol