  We report the discovery of a possible planet in microlensing event
MOA-2010-BLG-353. This event was only recognised as having a planetary signal
after the microlensing event had finished, and following a systematic analysis
of all archival data for binary lens microlensing events collected to date.
Data for event MOA-2010-BLG-353 were only recorded by the high cadence
observations of the OGLE and MOA survey groups. If we make the assumptions that
the probability of the lens star hosting a planet of the measured mass ratio is
independent of the lens star mass or distance, and that the source star is in
the Galactic bulge, a probability density analysis indicates the planetary
system comprises a 0.9^{+1.6}_{-0.53} M_{Saturn} mass planet orbiting a
0.18^{+0.32}_{-0.11} M_{sun} red dwarf star, 6.43^{+1.09}_{-1.15} kpc away. The
projected separation of the planet from the host star is 1.72^{+0.56}_{-0.48}
AU. Under the additional assumption that the source is on the far side of the
Galactic bulge, the probability density analysis favours a lens system
comprising a slightly lighter planet.
