Are you talking about the switches, and if so, only the MX variant, or the keyboards made by Cherry?
The MX switch itself was never changed much, they tried out different sliders and springs (I guess the first slider/spring combo they had was MX Black as you usually find these on older keyboards, there's also vintage Blues and Browns though) and around 1991 they changed the logo slightly, mainly making it smaller. Apart from that I don't think the switch design itself has ever changed.