  We suggest the ratio of the $\psi''(3770)/\psi'(3686)$ production cross
sections as an unambiguous probe of the dominance of hard, point-like physics
in charmonium production. If hard physics dominates the charmonium production
the ratio : ${\sigma(\psi'')\over\sigma(\psi')}\approx {\Gamma(\psi''\to
l^+l^-)\over \Gamma(\psi'\to l^+l^-)} \approx 0.1$ is independent of the
process. We argue that since the dominant $D\bar D$ decay mode of the
$\psi''$-meson can be detected with a high efficiency at the current facilities
the effective counting rate for the $\psi''$ production should be comparable to
that of the $\psi'$ and hence it could be observed at the $B$-factories. Even
in hadron induced processes the ratio will not be changed significantly by
final state interactions due to the similar mass and size of these two
charmonium states. A possible exception are the charmonium state interactions
with low energy particles -- comovers -- which are especially relevant for the
heavy ion collisions.
