More info on this:
My 280SL currently has a 4-speed trans and there's no indication that the car was originally a 5-speed. I was just hoping that maybe it was and a prior owner then changed it.
I don't have the data card to check for the "230" code indicating a ZF 5-speed trans. The data plate attached shows only code "620" for Italy.
Joe Alexander was very helpful in providing some good info on this, particularly that a conversion from 5-speed to 4-speed or vice versa, would have involved a lot of work and expense for a prior owner as well as for me now.
If anybody has a picture of a data card with the 5-speed option or a picture of a data plate indicating this, I'd like to see it.
Thanks!