As the saying goes, Ship Happens. Sometimes, worse then others. In todays case, this is a piston and rod on display at the Hoosier Valley Railroad Museum from Erie Lackawanna 310, an Alco S1. The engine in case is an Alco/McIntosh & Seymour 539, a 4 stroke engine with a 12.5″ bore and a 13″ stroke. A valve dropped while the engine was running, and decided to do a little dance in the cylinder.

http://www.hoosiervalley.org/