Hello, who could help me: There are a lot of changes at the numbering-plan of the swedisch engines over many years. Who has information? For example: SJ Z4 (XIII) ->1956 SJ Z42 -> 1958 SJ Z3 (IX) and so on … What was the reason? Have anybody a list about this changes?

I can not give you the reason for all these changes but you can find a complete list of all the swedish Z-engines (lokomotors) here: www.svenska-lok.se/motor_main.php?s=21