One of the zilches has been rediscovered. This is the zilch called "optical chirality", named by Tang and Cohen, since this zilch determines the degree of chiral asymmetry in the rate of excitation of a small chiral molecule by an incident electromagnetic field. A further physical insight of optical chirality was offered in 2012; optical chirality is to the curl or time derivative of the electromagnetic field, what helicity, spin and related quantities are to the electromagnetic field itself. The physical interpretation of all zilches for topologically non-trivial electromagnetic fields was investigated in 2018.