This is one of those topics that starts with an easy question and then becomes complicated.
This time it develops into a story about the evolution, or more accurately, the apparent degeneration of a useful part during the W113 production run.
Originally, the parking brake cable was fixed to the rear axle using an O-ring attached to a simple cable clip mounted near the cross arm. Those 2 items were part of Group 42 - the "hand brake" [upper left panel in picture]. The clip was p/n 303 995 0720. (It was used also on trucks) and the O-ring was p/n 136 997 02 40.
A bit later MB decided to change the clip to something more complicated and it became part of Group 35 - "rear axle" - with a new p/n: 113 995 0040 [#146 in the lower middle panel].
However, the O-ring that holds the cable remained in Group 42 with a new p/n: 136 997 02 41 [upper middle panel].
Curiously, by the time Edition C of the parts book was printed in Jan. 1967, the p/n for #146 had already been changed to: 000 137 010200 - and was now called a "spring washer" !! - although the picture in the book still shows a clip.
By the time the 250SL/280SL parts book was printed, #146 had indeed degenerated into a spring washer [right panel] and the new p/n is 000 137 010201.
The problem is the O-ring [#42] is still listed in Group 42 [upper right panel] - but what holds it and the cable up??
Any 280SL owners out there who can tell us how their hand brake cable is attached??So next time you call a vendor to order a part and wonder why it takes the person a long time to find it (or never) now you know why. I certainly would not have gotten that far without the help of parts guy "numero uno", Dave Gallon, who informed me about the Group change for #40 -> #146.