I think it's supposed to be this type:
http://catalog.eautopartscatalog.com/mercedesshop/sophio/quote.jsp?clientid=catalog.mercedesshop&cookieid=1VC0GXUSV1VC0H5JOA&baseurl=http://catalog.peachparts.com/&partner=mercedesshop&year=1988&product=J4070-44817&application=000046642
Not 100% sure though. The type you show I don't see what holds it in place, unless there is a slight outer groove. The one I link you to there is a deep outer groove that holds it on to the lever.
(I used a 1988 300E as an example to try finding the part I thought you need, just so you know why it's showing the part for a 300E)
Gilly