I'm not sure if the first two are identical, but 10203 was an improved loco finished a few years later. It was a little stronger than the others, at 2,000 hp, which brought it a little closer in power to the bigger steam engines of the day. I remember reading in Hornby Magazine that it was the first locomotive that could be classed as a Type 4 (2,000-3,000 hp) in Britain. Can anyone else help with more info?