When goods are delivered to the buyer on approval or "on sale or return" or other similar terms, the property therein passes to the buyer
         (a) when he signifies his approval or acceptance to the seller or does any other act adopting the transaction;
         (b) if he does not signify his approval or acceptance to the seller but retains the goods without giving notice of rejection, then, if a time has been fixed for the return of the goods, on the expiration of such time, and, if no time has been fixed, on the expiration of a reasonable time.