Date registered: May 2016
Vehicle: 2000 S430, 2003 S430, 2003 S600 TT, and 2005 E320 CDI
Mentioned: 170 Post(s)
Quoted: 962 Post(s)
My first guess would be that the strut from the 2006 S-class was on its way out already. As far as fitment, if your 2000 S500 is a 2WD car, then the struts are the same for any 2WD W220. In the USA, that means model years 2000 through 2006 (Europe had W220's in 1999, I think).
Question for the OP: might this 2006 strut be from a 4-Matic?
If so, then question for the forum: are AIRmatic struts for 4-Matics different somehow from the non-4WD cars, and if so, is it in any meaningful way?
2000 S430 (Dad's car, used for special occasions)
2000 S500 (wife's DD: my first W220 project car)
2003 S600 ("sex on wheels"--second w220 project car)
2003 S430 (one of two current DD's--third W220 project car)
2005 E320 CDI (the other current DD--first W211 project car)