You may be thinking of the term "Grease Zerk", this is the fitting on a coupler or joint that a grease gun is connected to. Nope, MB ain't had in in so long, not even mentioned in the maintenance manuals. I think maybe around 1970 or so they went to maintenance free front suspension parts. There just sealed really good to hold in the grease. Eventually the joint wears out just due to use, or the rubber boots either get torn or the rubber cracks due to age, then you replace the joint. If you tear a boot, they are available seperately. It doesn't really seem to me that this type of maintenance-free joint requires replacement any more frequently than a greaseable counterpart.
Gilly