Where a National Firearms Act stamp is destroyed, mutilated or rendered useless after purchase, and before liability has been incurred, such stamp may be redeemed by giving another stamp in lieu thereof. Claim for redemption of the stamp should be filed on ATF Form 2635 (5620.8) with the Director. Such claim shall be accompanied by the stamp or by a satisfactory explanation of the reasons why the stamp cannot be returned, and shall be filed within 3 years after the purchase of the stamp.