Industry 4.0 has revolutionized the way in which we relate to the industrial assets and production relationships. Focused on adapting technologies towards a digital transformation, its implementation brought several competitive leaps into product customization. The Digital Twin is a very powerful toll of this implementation, being able to simulate in real-time and make decisions based on real-world information as well as AI and business rules. However, and especially in developing countries, there are still barriers to establish Industry 4.0 both from a technical and an administrative standpoint. Interoperability of Legacy Systems and the investments needed for upgrades can make the reality of Industry 4.0 a distant future. To change that paradigm, research in Asset Administration Shell and the necessary adaptations of Legacy Systems is crucial to allow them the advantages of Digital Twins and the many features that can be implemented to enhance productivity and gain competitive advantages in a globalized scenario. This paper will focus on proposing a model based on AAS and other technologies from RAMI 4.0 that can be adapted to work not only with state-of-the-art equipment but with legacy systems as well. This model should work with future research to develop a solution to implement Digital Twin in Legacy Systems.