I recently found this neat error in a box of coins I hadn't looked at for a while. I didn't notice it before or I would have put it aside. Anyway, as you can see it's slightly larger in diameter than the regular dime probably due to the fact that the collar was way bigger that the dime one would have been. It's weighs a tenth of a gram less than a normal dime for some reason. I t's a nice BU coin. Regards, Mike
I see some copper showing on the Obverse picture. But please show the edge. If it is legit it would be a very rare find! @Pete Apple @JCro57 @Fred Weinberg And all other error specialists!
Die pressure for a nickel is higher than for a dime and since the blank didn't reach the collar, even less pressure is needed for a good strike. The only thing that would create a weak strike on this piece would be if the dies were adjusted to not close enough and since dies can hit each other when no blank is present, that doesn't seem to be the case.
This coin was almost certainly struck on a hydraulic press, for which the stroke would be greater, as controlled by feedback from the hydraulic pressure sensor. Therefore, the force imparted upon this coin would be the same as for thicker normal nickels which would expand completely into the nickel collar. Since the surface area of this coin is less than for a normal nickel planchet, the net striking pressure on its surface was actually higher than normal. This explains the exceptional detail we all see.
Wow! The feedback system for the hydraulics is fast enough to adjust the pressure on just one strike! I would have imagined that the system would have to monitor multiple strikes to make such an adjustment.
The high speed Schuler presses have a top stroke rate of 850 hits per minute. Depending on the frequency response of the pressure transducers (I don't know whose sensors they use, but I know DAC offers a model sampling at 50 KHZ) and the scanning / output rate of the controller (also not known, but for which many offered in the market are equally fast), the feedback rate per stroke would be roughly 1/2(50000/(850/60) = 470 cycles per coin. The pressure transducer senses the pressure and, 470 times per strike, sends a proportional output to the controller which backs the pressure off once the desired value is reached.
This is fascinating stuff and a thought occurred to me as I read this. Is it possible that the dies could clash in the areas where there was no metal flow on this planchet? Might coins struck going forward show this clash?
Since the dies came no closer together than the fields on both sides of the coin, I'd say no, no clashing of the dies took place.
I understand the feedback rate of electronics. I would have expected the rate for the actual hydraulics to be much slower because of fluid motion. Thanks for the information, very informative.
Hydraulic fluid is essentially incompressible, and is therefore a very stiff system. As concerns responsiveness, if you've used car brakes on ice and felt the rapid modulation of the hydraulics as the ABS takes over control, then you should pretty easily understand how rapidly the hydraulics can respond in the coining presses.
