Very nice, though a little bug eaten. These are very collectable, but I can't give you much of a value. The pictures are small but your stamps appear to be 1898 documentary (revenue) stamps. Those particular stamps picture the battleship Maine and were issued to help finance the Spanish American War. It was the Maine that was sunk in Havana harbour and started the whole conflict (though some blame William Randolf Hearst as well). The same design was also issued as Proprietary Stamps. Our revenue collecting friends here can be clearer on the difference than I can.