  We consider the experimental predictions of two {\em one-parameter} no-scale
$SU(5)\times U(1)$ supergravity models with string-inspired moduli and dilaton
seeds of supersymmetry breaking. These predictions have been considerably
sharpened with the new information on the top-quark mass from the Tevatron, and
the actual measurement of the $B(b\to s\gamma)$ branching ratio from CLEO. In
particular, the sign of the Higgs mixing parameter $\mu$ is fixed. A more
precise measurement of the top-quark mass above (below) $\approx160\GeV$ would
disfavor the dilaton (moduli) scenario. Similarly a measurement of the lightest
Higgs-boson mass above 90 GeV (below 100 GeV) would disfavor the dilaton
(moduli) scenario. At the Tevatron with $100\ipb$, the reach into parameter
space is significant only in the dilaton scenario ($m_{\chi^\pm_1}\lsim80\GeV$)
via the trilepton and top-squark signals. At LEPII the dilaton scenario could
be probed up the kinematical limit via chargino and top-squark pair production,
and the discovery of the lightest Higgs boson is guaranteed. In the moduli
scenario only selectron pair production looks promising. We also calculate the
supersymmetric contribution to the anomalous magnetic moment of the muon.
