The twistgrip and front brake lever are comparatively recent. I would reckon it has been run as a field bike, probably by youngsters, until it stopped. There's enough there to make a rebuild worthwhile.
Until his dying day, my Dad lamented having to leave a 16H that he rode through the war in Burma on the dockside in Bombay. Not allowed to bring it home. It was probably sold off as surplus for 50 rupees.