There is only one OMM which some currently list where the original
mintmark was for one mint and the primary mintmark is for a
different mint and both mintmarks are totally separated from
each other. CONECA has recently re-evaluated the 1956-D
OMM-001 and has delisted it as an OMM. A second separated OMM, the 1980-D&S OMM-001
was recently debunked as die damage.