How about this one?

[Cees Klumper]

Here's another one (hint: the white part is oftentimes missing):
Download Attachment: missing.jpg
67.71 KB
Cees Klumper in Amsterdam
'69 white 280 SL automatic

[n/a]

Looks like a brake switch.
Michael Penner

[hands_aus]

I agree
Bob(Brisbane,Australia)

[Cees Klumper]

This one was obviously too easy ! The white ring is missing on many of our cars (could be a different color) because it is plastic/rubber and becomes brittle over time. Once it comes off, the returning brake pedal produces a metal-to-metal clunk. Plus the pedal sits closer to the driver when at rest, causing you to have to move your foot at a sharper angle in order to apply the brake. They are NLA, but I found a remanufactured one. I did have to re-adjust the switch when I put the ring on, which was easy.
Cees Klumper in Amsterdam
'69 white 280 SL automatic