The switch from the hard pocket to the soft pocket on US cars was made during the 250SL production run beginning with chassis number 02980.
Engelen lists it as the first change among 23 total changes. Also the spare parts list [Edition C] for the 250 SL/280SL indicates that switch (footnote 5 in Group 72). For example, the left door lining p/n was 113 720 0570 (MB-Tex covered) and changed to 113 720 2170 for 250SL (043) and to 113 720 2970 for the later 280SL (044).
That switch apparently was not made on European 250SL cars and if it was ever made on Euro280SL then perhaps only at the end of the run, or perhaps to some countries only. I believe that Sweden for example had different safety requirements, maybe Hans can add to this.
The fixing screw shown on John's 250SL was used on all doors with hard pockets although it is not clear from the Edition A of the spare parts list for the 230SL whether very early models had the screw and the bar inside to attach it to.
Since the driver side door has no grab handle the pocket is sometimes used to close it and that screw provides additional anchoring, however, it should be on both doors.
The p/n for the sheet metal screw: 007 983 004251 and for the countersunk washer: 900 056 004508.
There is a vertical bar attached to the door frame with a hole at the bottom to accept the screw.
But is not always easy to find it behind the panel!
