An omission in Special Relativity

In Special Relativity there are infinitely many equivalence classes of frames of reference. In each such class every two frames of reference move uniformly with respect to one another. It appears that the following questions have never been asked : In which of such equivalence classes of frames of reference is Special Relativity supposed to hold ? How can we identify such a class, and do so theoretically or empirically ? 1. Equivalence classes of frames of reference The two principles of Special Relativity, Einstein [2, p. 39], Durell [p. 30], are : 1. There is no absolute motion. Consequently, it is not possible to detect uniform motion. Furthermore, in two frames of reference which move uniformly with respect to one another, the laws of physics are the same. 2. In all forms of wave motion, the velocity of the wave propagation does not depend on the velocity of the source. Consequently, the velocity of light propagation in vacuum does not depend on the velocity of its source.