There is no antena switch in a 91.

The only difference in value between an 89 and a 90 is that an 89 seems like a 20 year old car and a 90 seems like a 10 year old car. It's just generic valuation math. Kinda like Honda math that says two 5HP engine mods = a 10HP rise in wheel HP A 91 might have special value because it was the last year of the W126 in the US but I doubt KBB's valuation logic is that precise.

Sixto
95 S420
87 300SDL