Since the design rim is well struck, the rim/edge junction sharp, and the edge presumably flat, it would be a filled die error (a.k.a. "grease strike").
Yeah, I knew it was a die fill, but a die trail would be nice. I have found less filled coins that seem to match this one. I could put together a progressively filled die set on this one year issue. Now I have to break open all my hundred rolls to look for more. BTW I have found way more errors than high quality MS coins, funny, thank you mint.
First of all, you must disabuse yourself of the notion that there is such a thing as an identifiable "die trial". While die trials do exist (at least inside the Mint), there's no way to distinguish a weak strike generated during a test run from a weak strike caused by spontaneous equipment malfunction. A weak strike is simply that -- a weak strike. There are two proximate causes for weak strikes. 1) Insufficient striking pressure. 2) Insufficient die approximation with normal striking pressure. There are perhaps a dozen ultimate causes for weak strikes. In a simple weak strike, it is impossible to determine proximate cause, let alone ultimate cause. My extensive studies of multi-error weak strikes indicate that the vast majority of ordinary weak strikes are due to spontaneous equipment malfunction and are also mostly due to insufficient die approximation. The dies are out of adjustment, or are being held apart, so that at their closest approach, they are barely closer than the thickness of a planchet.
