That's part of the fun, you have to discover these things as you go. I'm sure most of the people who buy new MB's don't really care what gear they're starting out in, they're probably rich folks who lease a new one every 2 years.
I'm curious, but what are the 1st 2nd and 3rd gear speed limits on your 88 420SEL? I'm not sure why, but they seem to vary, even within the same model year.
2003 S500 Black/Charcoal
1990 560SEL 61k Arctic White/Grey
1988 420SEL Black/Palomino Sold @ 85k
1987 420SEL Midnight Blue/Grey
1986 420SEL Diamond Blue/Grey
1983 380SEL Champagne/Palomino