They're better known as the R171 SLK. By 05 they were beginning to get on top of the rust issues that plagued the R170s but they are still a long way from being good. Look in particular at the rear arches and by the boot handle.
Look everywhere on them. A car dealer friend had one over and it was terrible once you'd lifted the bonnet or looked underneath and opening panels. I still smart over the W209 CLK I had, another MB that seems to instantly dissolve.
