I believe it is item 5 in the first picture below. Let me know if you need more info because I have this ancient Bosch document which deals with our older cars. The second pic is from the FSM, in case that is helpful.

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1968 220D, w115, /8, OM615, Automatic transmission.
My 1987 300TD wagon was sold and my 2003 W210 E320 wagon was totaled (sheds tear).

Thank you for posting that first image.

The same illustration is in my copy of the factory service manual but for some reason the parts listing was omitted in the Mercedes publication.

By comparing your image with the diagram I posted it appears part number 33 is the clip I'm hunting for.