Marklin is the fan-made term for a black tank engine who was used for moving background rolling stock in the first season. His model was based upon the BR 80 heavy-duty tank engines used primarily in Germany and Poland.
Marklin was first credited in the crewmembers' dedication page on the Sodor Island Forums website. The page featured a "behind the scenes" photograph of Marklin in Tenders and Turntables. Marklin appeared on screen in The Flying Kipper and was one of the tarped engines in Trouble in the Shed.
Some think that Marklin was modified for use as Puffa or the goods engine in TUGS. And although Puffa's cab resembles that of the BR 80, it is possible that another BR 80 model was used to make Puffa as the BR 80 is the most widely-produced Marklin model. As of now, nothing has been confirmed.