The initials MKS are found in the following contexts:
- an MKS logo appears on the Mizuho Six — it certainly refers to the manufacturer Mizuho Kōki Seisakusho;
- MKS shutters are found on the Mizuho Six and reported on the Mihama Six — these were certainly made by Mizuho too;
- an M.K.S engraving appears on the subminiature Robin — this certainly explains why the camera is attributed to "M.K.S. Co." in Sugiyama, but the actual meaning is unknown.