English: The top controls on an early-model Pentax LX 35mm film camera, showing the original design of the shutter release button lock mechanism (center), pictured in the unlocked position. The switch would be turned toward the shutter speed dial to 'lock' the button, preventing accidental presses. The lock mechanism was, at some point, redesigned for the late-model LX. There is no official distinction between the early and late models, so the slight differences in appearance were noted by third-party users.