Part V: Planchet Errors:
Upset Mill Errors:
Abnormal Upset
Definition: This anomaly is visible only on unstruck planchets and off-center strikes. Affected planchets carry a pattern of upset that is distinctly different from other planchetsof the same denomination and time period.
Possible causes for abnormal upset are:
1. A worn or damaged groove in the upset mill.
2. Improperly machined grooves
3. Use of upsetting equipment intended for a different
denomination (domestic or foreign)
4. Use of upsetting equipment with grooves of an experimental nature
5. Circumferential pre-strike damage that resembles the effects of upsetting
The appearance of abnormal upset is highly variable and suggests many different causes.
Note: Several Examples are shown below.
Depicted below is an undated, off-center nickel showing an unusually prominent proto-rim, a very wide bevel, and a thin, flattened center strip along the edge. Nickel planchets generally show a very low proto-rim, a very short bevel (or one that is entirely absent), and a broad, flat edge.
The three images below depict an undated, off-center nickel that may not even have been struck on a nickel planchet. The leaden gray color, matte interior texture, and complete absence of tumbling marks suggests an unexpected origin and an unorthodox entry into the production stream. In any case, the pattern of upset (if that’s what it is) is bizzare. The proto-rim is broad and tall and has a sharp internal margin. A thin, pleated apron extends in from the internal margin of the proto-rim and rests lightly on the planchet’s surface. The upper/outer surface of the proto-rim shows a broad slope that almost looks machined. The edge is smooth and strongly convex.
The pleated apron suggests that this is a form of circumferential pre-strike damage, and not any intended style of upset.
