Where a patent has been restored, any person who, during a period starting 6 months after the lapsing of the patent, has expended any money, time or labour in view of making, using, exercising, offering to dispose of, disposing of or importing the invention, may apply in the prescribed manner to the Commissioner for compensation in respect of the money, time and labour so expended.  The Commissioner may, after hearing the parties concerned, assess the amount of such compensation if in his opinion the application ought to be granted and determine the time within which such compensation shall be paid.   Any amount so assessed shall not be recoverable as a debt or damages but, if it is not paid within the time determined by the Commissioner, the patent shall lapse.