Part V: Planchet Errors:

Blanking and Cutting Errors:

Definition: Any error that can be traced back to 1) the blanking press, 2) the shears, saw, or guillotine that trims the ends of the coin metal strip, or 3) the splitter that divides the coil of coin metal into narrower strips.

Special Note on clipped coins;

Because this sub-section of the Error-Variety Ready Reference is dedicated to “clipped” error coins, it is worth mentioning several diagnostics useful for distinguishing the genuine article from a tampered coin:

1. Blakesely effect. This can potentially develop on any coin struck on a blank whose circular outline is interrupted for any reason, provided that the interruption appeared before the blank entered the upset mill.

The Blakesley effect is located at the pole opposite the deficit. It consists of 1) weakness or absence of the design rim combined with, 2) an especially well-struck edge.

The Blakesley effect reflects the fact that this area of the planchet was never upset. The deficit at the opposite pole prevents the upsetting mill from squeezing the planchet at this point and pushing up a proto-rim.

The Blakesley effect is not always present, especially when the deficit is very large. In the latter case, effective striking pressure is high enough to cause coin metal to completely fill the rim gutter of the die. Effective striking pressure is increased because the entire tonnage of the strike is concentrated on a piece of metal whose area is substantially smaller than a normal planchet.

2. Fade-out and taper of the design rim as it approaches the clip (most clip types will have this feature).

3. “Cut-and-tear texture” on the exposed edge of the clip. Only curved clips and elliptical clips will have this feature. It is also referred to as a “breakaway zone” or a “belly line”. The cut-and-tear texture refers to the microscopic texture of the clipped edge. Part of it is smooth, while part of it is grainy. The grainy part tells you that this was the original bottom of the coin metal strip. As the blanking die (punch) penetrates the coin metal strip, it forces a blank through a hole in a perforated base plate. The sharp, right-angle edge of the blanking die slices through the upper part of the coin metal strip. The lower part of the blank simply tears away from its hole in the coin metal strip as it is pushed down by the flat face of the blanking die.

4. Reversal of position of exposed copper core. This pertains only to curved and elliptical clips in clad issues. In a clad coin, the copper core is asymmetrically exposed along the edge. The position of the exposed copper core “flips” when you transition from a normal edge to the clipped edge. The reason is simple: the normal edge represents the edge of the blank, while the clipped edge represents the edge of the hole.

As the blanking die pushes a blank through the hole in the perforated base plate, the edge of that hole drags the bottom clad layer onto the edge of the blank for a short distance, partly hiding the lower portion of the copper core. Simultaneously, the edge of the blanking die forces some of the top clad layer down onto the edge of the hole in the coin metal strip, partly hiding the upper part of the copper core.

5. Metal flow in design elements bordering the deficit. Metal flow refers to a distortion and stretching-out of letters, numbers, and any other raised feature. It is caused by coin metal “squirting out” beneath the dies.

6. Proper curvature for the type of clip. Be aware that striking pressure and the expansion of the coin can alter the shape of a clip, sometimes drastically. This is especially true if clip is large and if the coin is struck out-of-collar.