The Gillette Psycho Safety Razor was used in US Mental Hospitals or Prisons but it needs a special key to access the blade
This razor was made especially for Mental Hospitals or Prisons where the inmate would not be granted access to a razor blade. They needed a way to control access to the blade, so the Psycho Tech was born. Nurses or guards would change out the blades for the inmates, lock the cap down, and keep the key.
As these razors were provided in boxes of ten and each inmate would not keep their own key, there was usually fewer keys than razors. This is a challenge for people collecting these razors today as extra keys are needed. Razor Emporium shows in this video how they go about making quality replicas of these keys complete with boxes that resemble the original.
Watch at https://youtu.be/nQyByfxzfik