  2MASS J03202839-0446358AB is a recently identified, late-type M dwarf/T dwarf
spectroscopic binary system for which both the radial velocity orbit for the
primary and spectral types for both components have been determined. By
combining these measurements with predictions from four different sets of
evolutionary models, we determine a minimum age of 2.0+/-0.3 Gyr for this
system, corresponding to minimum primary and secondary masses of 0.080 Msun and
0.053 Msun, respectively. We find broad agreement in the inferred age and mass
constraints between the evolutionary models, including those that incorporate
atmospheric condensate grain opacity; however, we are not able to independently
assess their accuracy. The inferred minimum age agrees with the kinematics and
absence of magnetic activity in this system, but not the rapid rotation of its
primary, further evidence of a breakdown in angular momentum evolution trends
amongst the lowest luminosity stars. Assuming a maximum age of 10 Gyr, we
constrain the orbital inclination of this system to i >~ 53 degrees. More
precise constraints on the orbital inclination and/or component masses of 2MASS
J0320-0446AB, through either measurement of the secondary radial velocity orbit
(optimally in the 1.2-1.3 micron band) or detection of an eclipse (only 0.3%
probability based on geometric constraints), would yield a bounded age estimate
for this system, and the opportunity to use it as an empirical test for brown
dwarf evolutionary models at late ages.
