CPV code 50750000 designates Lift-maintenance services in the Common Procurement Vocabulary (CPV 2008), the EU classification used to describe the subject of public contracts.
50750000 is a leaf code — the most specific level of its branch — so it can be used directly as the main CPV code of a contract notice. If it does not quite fit, check the neighbouring codes under 50700000 (Repair and maintenance services of building installations).