@sbg, the best way to figure out if you have a coin showing a die clash is to look at an overlay to figure out if any detail from the other side might line up with the odd marks. This isn't a 100% methods, but works in the overwhelming majority of cases.
"If you climb a good tree, you get a push."
-----Ghanaian proverb
"The danger we all now face is distinguishing between what is authentic and what is performed."
-----King Adz