VVV J12564163 - 6202039 is an L subdwarf located in the Galactic plane ( b = 0 \fdg 831 ) discovered by its high proper motion ( 1.1 arcsec yr ^ { -1 } ) .
We obtained an optical to near-infrared spectrum of it with the X-shooter on the Very Large Telescope , and re-classified it as an sdL3 subdwarf .
Its best-fitting BT-Dusty model spectrum has T _ { eff } = 2220 K , [ Fe/H ] = -0.9 , and log g = 5.5 .
It is just below the stellar/substellar boundary in the T _ { eff } versus [ Fe/H ] parameter space .
This object is at a distance of 66.94 ^ { +8.49 } _ { -6.77 } pc according to the Gaia astrometry .
It has a halo membership probability of 99.82 per cent according to its Galactic kinematics .
It has unusually flat ( | Z | \la 500 pc ) and extremely eccentric ( e = 0.9 ) prograde orbit that takes the source from as close as 1.2 kpc from the Galactic centre to 24 kpc out .
VVV J12564163 - 6202039 joined by SDSS J133348.24+273508.8 and ULAS J021258.08+064115.9 are the only three known objects in the sdL subclass that have halo kinematics .