shadowfox
Darkroom printing lives
Mamiya/Sekor 528 TL AKA Sears TLS Auto 500 ??
Good guess.
But the camera in question has a set of interchangeable lenses designed for it. And I'm talking about quite a few lenses, not just the triad-focal-length selection like Kodak Retina (Reflex) or Olympus Ace.
Hint #3: A rare adapter would allow some M42 lenses to be used on this camera.