cover Thompson, John L., 1c Black (RS242 var.), issued stamp design printed on message side of 1c Brown on buff postal card (UX3), postmarked Troy, N.Y., reverse is titled 'Test of Counterfeit' showing a reproduction of the company's M & M stamp which must be present on all genuine bottles of Dr. Isaac Thompson's Celebrated Eye Water, printed in Blue & Black, text cautions against counterfeits and imitations, very faint thin toning band on reverse, otherwise extremely fine photo est.