Given the task definition and input, reply with output. Given a context passage, generate a question from the passage such that its answer is shortest continous span from the passage.

The Caledonian Railway 179 Class (nicknamed Oban bogie) was a class of 4-4-0 steam locomotives designed by George Brittain for the Caledonian Railway (CR) and introduced in 1882.
Which was the official year for the approval of Caledonian Railway 179 Class?