What is strike/ejection/machine doubling?
Lewy
Posts: 594 ✭
Morgan dollars is my main focus on this subject, but the same principles and terms might apply to other coins as well?
What is the difference between machine doubling and strike doubling?
Are there still more different types of doubling other than what is found on the dies themselves?
Most importantly, does there seem to be a prevalence to machine/strike doubling in either weakly or strongly struck coins? On coins of certain years or mints? Does there seem to be a connection anywhere?
I have also heard of a thing called 'ejection doubling'.... what is that? Is it predominantly only on the reverse or can it be on the obverse as well?
What is the difference between machine doubling and strike doubling?
Are there still more different types of doubling other than what is found on the dies themselves?
Most importantly, does there seem to be a prevalence to machine/strike doubling in either weakly or strongly struck coins? On coins of certain years or mints? Does there seem to be a connection anywhere?
I have also heard of a thing called 'ejection doubling'.... what is that? Is it predominantly only on the reverse or can it be on the obverse as well?
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Machine doubling is subject to any coin that has been struck with a mechanically driven anvil & hammer, from cents to dollars. Screw type presses did not create this effect, because the operation is much slower and deliberate.
Vibrations in the press can cause tightened fittings to become loose or out of adjustment, and as the planchet is struck, there is a slight shift which can be seen mostly on the numbers and letters. The shelf-like appearance, which is periodic in nature, is a dead give away that you have machine doubling and not a doubled die that would appear exactly the same on every coin.
There is no rhyme or reason for machine doubling to be more prevalent on the obverse or reverse, it can happen to either side and is random in nature.
Of course corrections are always encouraged.
"Keep your malarkey filter in good operating order" -Walter Breen
They all happen when the coin is struck and might be caused by a die that's loose or a coin that bounces back into the die as it ejects.
These are all strike errors.
(most likely these add no premium)
Doubled dies are created when the die is made so all coins from that die will have the same doubling and can't make any normal coins.
They are die varieties.
(adds some premium)
Some other types of doubling that are different would be:
A double struck coin, when the coin gets fully double struck and could be rotated or even flipped in between the strikes.
These are strike errors.
(adds some premium)
Abrasion doubling is most likely from polishing or cleaning the die.
These are more like die states, if extreme they might be considered an error.
Someone might call it a variety since all coins from a certain point will have it the same but it wasn't on the die when it was made so I wouldn't call it a die variety.
(might add some premium)
Erosion doubling or die fatigue is from wear to the die from the metal flowing from use. It often shows going to the rim or away from the details in both directions.
These are more like die states, if extreme they might be considered an error.
(might add some premium but not likely)
Longacre doubling only shows on some of his designs. It might be designed into the coins or it an artifact of the way they made the dies.
(no premium, it's normal)
<< <i>Most importantly, does there seem to be a prevalence to machine/strike doubling in either weakly or strongly struck coins? On coins of certain years or mints? Does there seem to be a connection anywhere? >>
Some coins/years have a lot of it like 53-57 cents were plagued by it. Maybe at certain points the mint didn't keep things maintained well or they were in a frenzy to pump out a lot of coins.
I'm not sure if weakly or strongly struck matters but for abrasion or die fatigue doubling it would be most likely on a well used die.
Feel free to add or clarify this
The duplicate machine is usually put in an inconspicuous spot so the workers won’t notice what has been going on. This happens in the Navy, too. But it has a different name.
I do appreciate it..... everyone.
...some stuff here, lewy. link 1 link 2 hope this helps.
<< <i>Hmmm….”Machine doubling” occurs late at night, when all the workers have gone home and the guards are munching donuts and drinking coffee. Two of the machines will get together, watch videos about oil and lubricant and gears and screws and other dirty stuff, and then make a duplicate. This is called “machine doubling.” >>
I think I saw a cartoon version of this made in the 40's right after WWII, I think it might have inspired "Night at the Museum"
"Keep your malarkey filter in good operating order" -Walter Breen
<< <i>I have also heard of a thing called 'ejection doubling'.... what is that? Is it predominantly only on the reverse or can it be on the obverse as well? >>
Ejection doubling is where the metal of the design elements are pulled sideways and upwards as the coin is dragged away from the die during ejection. I'm not qualified to say if it's most predominate on the rev or obv.
Two forms are recognized. "Push doubling" involves a bounce of the die and produces marginal shelving. No bounce occurs in "slide doubling". Here the design is smeared. Some slide doubling can be caused by a coin sticking during ejection, but it is indistinguishable from slide doubling caused by die movement.
Most cases of machine doubling are due to a loose or vibrating die or an unstable die assembly. It can occur on the obverse face, the reverse face, or both faces simultaneously. You can have up to four staggered sets of shelves on one face. Machine doubling in two or three different directions can occur on the same face.
I find it a rather interesting phenomenon, especially in its most severe forms.
<< <i>You can have up to four staggered sets of shelves on one face. Machine doubling in two or three different directions can occur on the same face. >>
I would find that highly interesting..... any idea as to where I might find images?
Thanks again everyone !
...i thought my links had some, lewy. perhaps i'm mistaken.
Thanks for the photos..... I do very much appreciate them.... Have you seen the four stage doubling or the multi-directional effect that errormaven spoke of ? Those are what I am attempting to hunt down images of now.
...here's another link lewy. it may help you further in
your knowledge of this subject.
--Severian the Lame
Cheers!
Kirk
P.S. Thanks for posting Lewy, this has been a very educational thread with all the responses!
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BONGO HURTLES ALONG THE RAIN SODDEN HIGHWAY OF LIFE ON UNDERINFLATED BALD RETREAD TIRES
Weiss, what a coin.... Is that S tripled? It sure looks like it from my house.
I've been gone from here for a while..... kinda forgot what I have been missing at this site .... (Oh yeah, the people, the sharing, the silliness)... I think I'll hang out for a while.