  The field identification problem, including fixed point resolution, is solved
for the non-hermitian symmetric $N=2$ superconformal coset theories. Thereby
these models are finally identified as well-defined modular invariant CFTs. As
an application, the theories are used as subtheories in tensor products with
$c=9$, which in turn are taken as the inner sector of heterotic superstring
compactifications. All string theories of this type are classified, and the
chiral ring as well as the number of massless generations and anti-generations
are computed with the help of the extended Poincare polynomial. Several
equivalences between a priori different non-hermitian cosets show up; in
particular there is a level-rank duality for an infinite series based on $C$
type Lie algebras. Further, some general results for generic $N=2$ cosets are
proven: a simple formula for the number of identification currents is found,
and it is shown that the set of Ramond ground states of any $N=2$ coset model
is invariant under charge conjugation.
