It's a 240D
Man I bought it from was a diesel fanatic, told me I should check the chain NEXT YEAR.
Only put on about 4000 miles since purchase.
I did a considerable amount of reading here before attempting this task, saw where a new chain will 'break in' 2 degrees.
I saw nothing mentioned about 'caution' for a previously installed key.
It may be old news for you guys but a rookie on these things looks for any guidance he can get.