CPV code 76431600 designates Well-drilling rig monitor services in the Common Procurement Vocabulary (CPV 2008), the EU classification used to describe the subject of public contracts.
76431600 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 76431000 (Well-drilling services).