Is It Okay For Me To Turn Off A Thermostat Which Looks As Though It's Not Been Touched In 20 Years Or More?

[roastbeefready]

Strange question right? And probably dumb. But that's how it looks with it looking all very dusty and the one I'm looking at right now looks like the black and white ones I've not seen in years. Kinda like the one in the image provided, but with black on the top and on the bottom and white all over. I remember them first being installed in another property which was council owned in the very early 90s as a child. So its it safe to turn it off and on?