BB,
If you are interested in your car being as original as possible, look for a date (month/year) stamped on top of the booster. Mine had one. If it's there AND originality makes a difference to you, then you might want to get it rebuilt. Otherwise, replacement is the way to go.
Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both tops
1994 E420