Hi Malcolm,
well, really we will never know, just utilize the logic, if we assume the piece is original no sense for the artist (considering in general Japanese metal works, like for exemple the kozuka both sides or Tsubas) ,to let empty with no any decoration the reverse side...the Mt Fuji and all decoration look in armony with the main subject in front, and probably contain a message that Lord protect all Japan...This fanciful interpretation have the same value (really no much) to assume that the cross is original in front and the design of Mt Fuji made in Komai...
the true has gone with the artist...