It has, in fact, been L.Howe's paper [3] entitled "Symmetry between gravitational and electrical forces' on the website www.innovationgame.com/physics that made the author realize that the operation "sign inversion of mass" applied to classical mechanics and physics delivers "an isomorphism of theories" which is similar to the Dirac operation of inverting all quantum numbers of a matter particle (cf footnote 5 below). We show below that for the electron one needs on top of the sign changes also parity reversal.