On the calling card of "A. Coyle | Vienna". About 3 inches by 1-3/4 inches with curved corners. Presumably Vienna, 1897-1899.
This is simply Mark Twain's autograph signature, in pencil, on the reverse side of the calling card of "A. Coyle | Vienna". The city effectively dates the signature, at 1897-1899: Twain, his wife Olivia, and their daughters Clara and Jean went on an around-the-world lecture tour in 1895-1896 (for the purpose of paying off Twain's staggering debts, despite his personal bankruptcy in 1894). The family wound up in London, where they stayed for most of a year before departing in 1897 for what became almost two years in Vienna -- where they hoped Clara would be able to study piano under Theodor Leschetizky, and Jean would be able to see medical specialists for her epilepsy.
During his stay in Vienna and Kaltenleutgeben, Mark Twain, a prolific writer, continued writing stories, essays, and articles, some of which he never finished (not an unknown phenomenon for writers in Vienna). Amongst the work Twain started and did finish were: "What is Man?", "How to Tell a Story and other Essays", "Concerning the Jews", "The Chronicle of Young Satan" and the memorable "The Man That Corrupted Hadleyburg". His unfinished but eventually published Mysterious Stranger stories were set in old Austria...
(An aside: Clara Clemens met her future husband, Ossip Gabrilowitsch, in Vienna. Gabrilowitsch was a Russian pianist and orchestra conductor, who had also been a student of Leschetizky. At his own request, Gabrilowitsch was buried at the foot of Mark Twain's grave in Elmira, New York in 1936. He and his famous father-in-law share a monument erected by Clara.) [Dolmetsch]
We have been unable to determine who "A. Coyle" in Vienna was -- but since Twain's characteristic signature (with customary flourish) is in pencil, it is likely that it was prompted by a spur-of-the-moment request. Fine condition. Item #15102