I am writing a monograph about the only postage stamps ever printed in Denver, Colo., and Salvador Cataño made a "secret mission" on behalf of the Constitutionalists to place the order with Smith-Brooks Printing Company in March of 1914. The visit was noted by the Rocky Mountain News in an article on March 10, 1914.
O.L. Smith (founder of Smith-Brooks) son-in-law, Dr. Louis Hough, was a surgeon for the Mexican National Railway and made friends with Cataño. It was apparently through that connection that the order was placed.
The picture you have of Cataño with Carranza and the others provides proof that he was close to the the inner circle of the revolutionaries. It would provide an excellent element for the monograph.
I would appreciate it if you would consider sending me a copy.