Mechanical Doubling Doubled?

[JonMN34]

I thought this was an interesting coin.
The LIB of LIBERTY has Mechanical doubling but the "doubling" is "doubled"

Any thoughts? I've not seen a second "doubling" before

[mustbebob]

This actually happens with more frequency than you might think. This is sometimes referred to as die 'chatter'. Once the coin is struck, the die bounces microscopically a couple of times resulting in things like this.

[JonMN34]

Thanks Bob!

[JeanK]

I think these are fun coins to collect as errors. Yours is a good one.
Jean

[coppercoins]

The correct term is "machine doubling" - not "mechanical doubling". It's shorter, easier to say, and the accepted 'norm'.

[trails]

I have been looking into machine doubling that shows more than one step (or if you prefer, more than one hit).

First, let's look at what happens to create machine doubling. For machine doubling to happen, the coin must have some bounce or chatter so that it strikes the retreating die, causing some of the design elements on either or both faces to flatten out giving it the appearance of doubling. While we can see this happening with a single step machine doubling, it is very hard to imagine it forming multiple steps, similar to the example shown. The machinery is operating at to fast a speed for a coin to have multiple hits against a retreating die.

So, let us look at something a bit different. Every coin has a resonating frequency. This is the sound that you hear when the coin is dropped. That sound is produced by the coin vibrating against the air and then the air vibrating on your eardrum, which is analyzed by your brain as a sound. Now picture the coin bouncing into a design element when it is vibrating. The "one" hit will produce a number of shelves on that design element from the vibration in that coin. Since we are talking about a frequency of about 5000 per second, this is much faster than the mechanics of the coin press. So, what we may be looking at is "resonating machine doubling" instead of just machine doubling.

Just something to think about.

BJ Neff

[mustbebob]

OK BJ. You just froze my brain over

[fugnchill]

Sweet...Harmonic Doubling. Sounds like a $50 coin on ebay to me.

Can't MDD be caused prior to the strike? Planchet sitting slightly at an angle but flattens at initial contact. I think I remember Mike Diamond describing different forms of MDD. (sliding into place and die bounce).

I'm just straining to use my memory

Lestrrr

[RWBILLER]

Hi:
That's a cool error. I have never seen that on a coin. I learned a new term, "Die Chatter."
Thanks
Roger

[coppercoins]

BJ seems to have WAY more time than I have going into the science of the whole thing. All I know is the difference between machine doubling and hub doubling and that machine doubling, unless really extreme, brings no premium value and is not widely collected. This is pretty much the way it goes, regardless of how many impressions the die makes to create the machine doubling.

[trails]

Your right Chuck, I do get carried away at times explaining how things may work.Looks like I even got Bob scratching his head on this one. It was something that came up between Ken Potter, Alan Herbert and myself as a possibility of happening and we all seem to think that it maybe the cause for multiple stepped machine doubling.

BJ Neff

[coppercoins]

I used to have a 1969 cent around here somewhere that had pronounced step tripling on it. Looked to me like a simple case of machine doubling with an extra bounce.

Oh...I remember now, I ran it on fleabay and sold it for a couple of bucks. No worries, another will show up some day.