So it seems someone thought fit to use a "protective sleeve" when they installed the water service. It just seems like madness to even
think about pitchy-patching galvanized pipe of that age. When you dig it up, you are likely to find a rusted lumpiness that can not be
unscrewed from any fitting (provided you can find a fitting) and cannot be threaded if cut. Plastic (PEX) is cheap and easy to install, and
is widely used for water service lines.