@1967Canadapenny - Aye there are on some of them very weak lettering, and also two different varieties of lettering I've noticed (one thicker, one thinner).
A "true godless dollar" (pardon me as I straighten my kilt...) has to be a President before William Henry Harrison (as that's when they moved "In God We Trust" to the obverse) and have missed the edge letterer entirely.
However they can miss the edge letterer in any year, or have the wrong edge lettering and are still worth a premium. :-)