The end-of-the-line of the Chartiers Branch was an engine servicing facility in Washington, PA. The facilities included a turntable, a three-stall rectangular engine house/repair shop, as well as the typical appliances, such as water spouts, a platform, etc. Some photos show a turntable cabin, while others show the turntable without one. It must have been added or removed at some point in time.
The "prr_panhandle_pa" Yahoo group's files section had a Microsoft Word document that shows a map of the area dated between 1857 and 1906. It clearly shows the turntable and engine house. It indicates that the turntable was 60 feet in diameter. There is a prototype photo showing a 4-4-0 steam engine with tender on the bridge with maybe 4 feet to spare, so that would confirm the 60-foot length of the bridge. Note the orientation of the diagram. Conventionally, it should be turned clockwise 90 degrees, to have the "north" arrow pointing up.