Real photo postcard image, captioned "U.S. Submarine in Pedro Miguel Locks". Number on side is S46; here's the link to the wikipedia article http://en.wikipedia.org/wiki/USS_S-46_(SS-157) although another source said launched in September 1925. There is no date on the postcard; it did, however, come from an album with several others and one shows the 'Carnival' parade in 1941, so I assume this image is from near that time, c1936-41 (and no earlier than 1930 as it has an "EKC" stamp box on the back which wasn't used before 1930.)