If it's an error, I would guess that a heavy grease strike-through is the most likely, but it could be other things like struck through a die cap. Standing by for pics...

In Memory of Crazyb0 12-26-1951 to 7-27-2020
In Memory of Tootallious 3-31-1964 to 4-15-2020
In Memory of T-BOP 10-12-1949 to 1-19-2024