In this paper, we present the prototype realization of the conceptual design of a fully-passive transfemoral prosthesis. The working principle has been inspired by the power flow in human gait so to achieve an energy efficient device. The main goal of this paper is to validate the concept by implementing in a real prototype. The prototype, in scale 1 : 2 with respect to the average dimensions of an adult human, is based on two storage elements, which are responsible for the energetic coupling between the knee and ankle joints during the swing phase and for the energy storage during the stance phase. The design parameters of the prototype are determined according to the human body and the energetic characteristics of the gait. The construction of the prototype is explained in details together with a test setup that has been built to evaluate the prototype.