There are not OMM on these coins. RPMs when out in 1990 when the dies included the the mintmark as part of the designs. Each mint makes there own dies now, so it is not possible to have OMM. If the mintmark is affected and the devices are afftected, you could have a doubled die. (All the doubling would be in the same direction of the design) but not possible to have a OMM since then. You could have Die Deterioration as an issue, but that would be a die event, not a die variety.