  For the Schr\"odinger equation $-d^2 u/dx^2 + q(x)u = \lambda u$ on a finite
$x$-interval, there is defined an "asymmetry function" $a(\lambda;q)$, which is
entire of order $1/2$ and type $1$ in $\lambda$. Our main result identifies the
classes of square-integrable potentials $q(x)$ that possess a common asymmetry
function. For any given $a(\lambda)$, there is one potential for each Dirichlet
spectral sequence.
