  The PS185 experiment at LEAR/CERN has investigated strangeness production in
antiproton-proton collisions with final states such as $\overline{\Lambda}
\Lambda$, $\overline{\Sigma}^0 \Lambda + c.c$, $\overline{\Sigma^+} \Sigma^+$,
$\overline{\Sigma^-} \Sigma^-$ and $K_S K_S$. Results are presented from a
study of about 32,000 {$K_S K_S X$} events obtained at several antiproton
momenta in the regions of 1.45 and 1.7 GeV/c. The $\overline{p} p \to K_S K_S
\eta$ cross sections extracted at these momenta constitute the first
measurement of this reaction in flight and are broadly consistent with
expectations of a phase-space extrapolation of branching ratios from
annihilation at rest.
