IBM model M keyboards are unique in that each one is individually labeled with a serial number and the “date of birth” is printed on the back. The Model M keyboard is a designation for a group of computer keyboards manufactured by IBM starting in 1984 Under each keyboard key there is an individual spring that when compressed converts physical …
https://www.amazon.com/IBM-Keyboard-Model-M-1391401/dp/B00F4FHY64

