Seiki Kogaku Co. (Japan) means "Precision Optical" and is a name used by more than one occasion by unrelated companies, including the one that made the early Canon cameras.
The Seiki 16 cameras use the Mamiya 16mm cassette were introduced in 1950 for the Japanese police.
Seek 25mm (f3.5-11) lens. Speeds of B, 1/25, 1/50, 1/100 . Tiny oval-shaped camera with focusing lens. Flash synch. Pop-up viewfinder at one end otherwise resembling the Scat.
Fixed-focus 25mm (f3.5-11) lens. Speeds of B, 1/25, 1/50, 1/100 . Odd-shaped squared off automatic pistol camera. Pop-up viewfinder on the top of the camera.