Undelivered postal articles which cannot be disposed of under the foregoing provisions, shall be detained in the office of the Post Master General for such further period (if any), and shall be dealt with in such manner, as the Central Government may, by rule, direct:
     Provided that--
         (a) letters and postcards shall be destroyed;
         (b) money or saleable property, not being of a perishable nature, found in any undelivered postal article, shall be detained for a period of one year in the office of the Post Master General, and, if on the expiration of that period no person has established his right thereto, shall, if money, be credited to the Post Office and, if saleable property, be sold, the sale-proceeds being credited to the Post Office.