The so-called Takahashi's \emph{Inversion Theorem}, the reconstruction of a given spinor based on its bilinear covariants, are re-examined, considering alternative dual structures. In contrast to classical results, where Dirac structure plays central role, new duals built using discrete symmetries $\mathcal{C}, \mathcal{P}, \mathcal{T}$. Their combinations also taken into account. Furthermore, ...