We present a Master equation for description of fermions and bosons for special relativities with two invariant scales, [Formula: see text], (c and λP). We introduce canonically-conjugate variables (χ0,χ) to (∊,π) of Judes-Visser. Together, they bring in a formal element of linearity and locality in an otherwise non-linear and non-local theory. Special relativities with two invariant scales provide all corrections, say, to the standard model of the high energy physics, in terms of one fundamental constant, λP. It is emphasized that spacetime of special relativities with two invariant scales carries an intrinsic quantum-gravitational character. In an addenda, we also comment on the physical importance of a phase factor that the whole literature on the subject has missed and present a brief critique of [Formula: see text]. In addition, we remark that the most natural and physically viable [Formula: see text] shall require momentum-space and spacetime to be non-commutative with the non-commutativity determined by the spin content and C, P, and T properties of the examined representation space. Therefore, in a physically successful [Formula: see text], the notion of spacetime is expected to be deeply intertwined with specific properties of the test particle.