  Superstring phenomenology aims at achieving two goals. The first is to
reproduce the observed physics of the Standard Model. The second is to identify
experimental signatures of superstring unification which, if observed, will
provide further evidence for the validity of superstring theory. I discuss such
potential signatures of superstring unification. I propose that proton lifetime
constraints imply that the Standard Model gauge group must be obtained directly
at the string level. In this case the unifying gauge group, for example
$SO(10)$, is broken to the Standard Model gauge group by ``Wilson lines''. The
symmetry breaking by ``Wilson line'' has important implications. It gives rise
to exotic massless states which cannot fit into multiplets of the original
unifying gauge group. This is an important feature because it results in
conservation laws which forbid the interaction of the exotic ``Wilsonian''
states with the Standard Model states. The ``Wilsonian'' matter states then
have important phenomenological implications. I discuss two such implications:
exotic ``Wilsonian'' states as dark matter candidates and ``Wilsonian'' matter
as the messenger sector in gauge mediated dynamical SUSY breaking scenarios.
