The S. Luna is a shutter mounted on several Japanese cameras of the 1950s. The "S" in the name probably stands for "flash-synchronized". The shutter was announced as a "T.S.K. Luna" in the user manual of the Cosmoflex II, certainly indicating that it was made by Tōyō Seiki Kōgaku and related to the TSK shutter. The speeds are B, 1–200. Two versions exist, with and without a self-timer.
Cameras fitted with an S. Luna Edit
Listing of a camera here does not imply that all examples were fitted with (S.) Luna shutters; merely that some examples were.