Who would have thought that the humble Brush Type 2 would end up being one of, or even the most tooled UK diesel loco in OO? Triang, Airfix, Lima, Hornby, Accurascale, and now Bachmann.
263 made and 64 years of service has a lot to do with it I'm sure.
I think possibly 42/43, 47 and 52 are onto four or five different toolings currently, depending on your defintion of OO.