By Mike Diamond for CoinWeek…
A rolling fold (also called a blanking burr) is a relatively rare planchet error that originates at the blanking press. Under normal circumstances, an array of cylindrical blanking punches (a gang punch) pushes its way through the coin metal strip as the strip advances beneath it. The punches are arranged in two to three staggered rows, allowing many blanks to be produced with each stroke.
Each blanking punch aligns with a slightly larger hole in a perforated base plate. Each hole is lined by a replaceable “thimble”. The punch’s force pushes a disc of coin metal into the hole. The disc, or blank, then drops through the hole and into a tote bin or conveyor that transports the accumulated discs for further processing.
Once in a great while, a blanking punch or a thimble becomes chipped or dulled, preventing the punch from slicing cleanly through the strip. If the chip or dulled edge is especially large, the punch will fail to slice through the strip completely, and the nascent blank will hang up in the hole. If, however, the chip is relatively small, the punch will tear through the thin connection that persists between the blank and the surrounding hole in the coin metal strip. The resulting blank will have a burr that sticks up from its upper face. This blanking burr is usually referred to as a rolling fold because it is folded inward as the blank passes through the upsetting mill.
The rolling fold is eventually struck into the planchet. It typically appears on the coin as a short, wide, symmetrical tongue of metal that intrudes a short distance into the field and is separated from the rest of the coin by a distinct fissure. Shown here is a rolling fold on the reverse of a 1964 Jefferson Nickel.
Since a rolling fold is generated long before the planchet reaches the coining press, its location relative to the design should be random. Rolling folds derived from the same chipped punch or thimble should match each other in size and shape but are expected to occupy an unpredictable position among the coins they appear on.
The non-repetitive positioning of a rolling fold seems to be initially supported by three 1967 Washington Quarters that carry a rolling fold derived from the same chipped punch or thimble. Specimen no. 1 shows the rolling fold on the obverse, with its midpoint at 7:30. Specimen no. 2 shows the rolling fold on the obverse, with its midpoint at 8:30. Specimen no. 3 shows the rolling fold on the reverse, with its midpoint at 9:00.
Although the positions do not exactly match, the three clock positions are closely bunched in vertical space. All appear on the left side, with midpoints lying between 7:30 and 9:00. Under conditions of perfect randomness, there is only a 1 in 64 chance of three same-source rolling folds falling within the same vertically defined 45-degree circle sector. This low-probability grouping suggests that we may not be dealing with perfectly random positioning.
The assumption of perfect randomness is thoroughly undermined by our next two specimens. These two 1972-D Jefferson Nickels display a same-source rolling fold at 10:30 on the reverse face. Under a scenario of perfect randomness, there is only a 1 in 720 chance that a pair of same-source rolling folds would occupy the exact same clock position on the same face.
I suspect that the rolling fold is directing the planchet to settle in a particular position, or at least within a narrow range of positions. Even though the blanking burr is folded inward by the upsetting mill, it still protrudes above the planchet’s surface. It’s possible that the burr is governing the orientation of the planchet as it drops into the feeder tube. It’s equally likely that the burr is somehow catching on the feeder and swinging around a pivot point created by the burr. In either case, the planchet will tend to settle consistently in the same location in vertical space.
I have a hunch that other planchet irregularities, such as certain forms of pre-strike planchet damage, can also guide a planchet into a particular position relative to the obverse and reverse designs. For example, these two 1999 cents—one struck in-collar and one struck off-center—show identical patterns of pre-strike damage in which part of the planchet was pinched off or sheared off before the strike. I have seen several other examples. This type of damage always, or almost always, appears in the northwest quadrant of the obverse face. This positional consistency originally led me to surmise that the damage was occurring immediately before the strike, which may indeed be the case. But it’s also possible that the damage occurred well before the strike and that the interruption in the planchet’s circular outline created an axis of rotation around which the planchet swung into a repeated point of rest. The fact that these two cents were struck by different die pairs adds a measure of support for this conjecture. If this severe and unusual pattern of damage were being generated just before the strike, the odds are the same press and the same die pair would be involved.
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The post The Case of the Non-Random Nickel: Rolling Folds Defy the Odds appeared first on CoinWeek: Rare Coin, Currency, and Bullion News for Collectors.
