Your grandmother lives in a cave?
Regarding the watch, it's an early 1970s Heuer Carrera 1553s with the Buren Caliber 15 movement.
http://www.onthedash.com/chronograph/carrera-reference-1553-s/
Value is very dependent on condition. Yours looks to be in reasonable condition aside from the dents on the side, probably needing a service, but will look much better after a crystal polish/replacement. The rest of the watch should not be touched or polished - cleaned only. And a movement service. I'd probably put the value at about £2000.