T217 is a set of 25 b&w cards of Pacific Coast League players issued by Mono Cigarettes in 1911. There are also at least 6 known nameless actress cards [image credit to Troy Kirk’s great Movie Card site].
Very little is known about the Mono brand. The first article ever published about the set (a 1-pager) was written by Mark Macrae for VCBC #4 in December 1995. Jon Canfield later shared some interesting research he did back in 2010. In the T card encyclopedia, Lipset noted that there were only 2 known complete sets and thirty years later, that may still be accurate.
Anecdotally, it seems that O’Rourke (not shown below) is scarcer than the other players, for reasons unknown. Also, since 12 of the 25 players were on Los Angeles, the worst team in the league, it may be that the set was distributed there.