These are window regulators:

http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1CQ0J3JZ41OF174BDV&year=1984&make=MB&model=300-SD-002&category=All&part=Window+Regulator&appChassis=_any

If you want the window to work, you pretty much need either a new or used part, unless you can fix the old one (unlikely). It's not very difficult to install in your car. I fixed one a few months ago. Some idiot put a piece of wood in the door to hold up the window in one of my cars.