The UNIDROIT Convention on International Interests in Mobile Equipment stands as one of the most ambitious and successful international harmonizing instruments on private law. The recent project to apply this Convention to mining, agricultural, and construction equipment (MAC Protocol) has encountered several challenging issues arising from the characteristics of the equipment and associated with the particularities of the finance praxis in the relevant sectors, and in particular, the delimitation of the scope that required formulation of innovative solutions. The aim of this paper is two-fold. Firstly, the paper analyses the delimitation of the scope of application in the MAC Protocol, revealing the underlying intricacies and explaining the resulting scoping mechanism. The solution adopted for the delimitation of the scope implies an original formula to define the covered equipment, an innovative mechanism to delimit the scope based on the use of Harmonised System codes, and relevant decisions on treaty design. As a consequence, the Protocol needs to provide for a very particular amendment mechanism. To that end, the current draft Article XXXIII was created. Therefore, secondly, the paper examines the amendment procedure incorporated in the MAC Protocol to that end in the light of treaty amendment practice and treaty design options, considering underlying policy concerns, and procedural alternatives to set a framework for the discussion of the draft Article XXXIII.