  A follow-up of a subsolar black hole candidate identified in the second part
of the third observing run of the LIGO-Virgo-KAGRA collaboration is carried
out. With a search signal-to-noise ratio of $8.90$ and a false-alarm rate of 1
per 5 years, close to the usual thresholds for claiming a gravitational-wave
event, we cannot exclude a noise origin. A complete Bayesian parameter
estimation of this candidate, denoted SSM200308, reveals that if the signal
originates from a compact binary coalescence, the component masses are $m_1=
0.62^{+0.46}_{-0.20} M_{\odot}$ and $m_2 = 0.27^{+0.12}_{-0.10} M_{\odot}$ (90%
credible intervals) with at least one component being firmly subsolar, below
the minimum mass of a neutron star. This discards the hypothesis that the
signal comes from a standard binary neutron star. The signal coherence test
between the two LIGO detectors brings support to a compact object coalescence
origin.
