  The high-magnification microlensing event MACHO-97-BLG-28 was previously
determined to be a binary system composed either of two M dwarfs, or an M dwarf
and a brown dwarf. We present a revised light-curve model using additional data
from the Mt. Stromlo 74" telescope, model estimates of stellar limb darkening
and fitting the blend separately for each telescope and passband. We find a
lensing system with a larger mass ratio, $q = 0.28 \pm 0.01$, and smaller
projected separation, $s = 0.61 \pm 0.01 $, than that presented in the original
study. We revise the estimate of the lens-source relative proper motion to
$\mu_{rel}=2.8 \pm 0.5 \; \mathrm{mas\: yr^{-1}}$, which indicates that 16.07
years after the event maximum the lens and source should have separated by $46
\pm 8$ mas. We revise the source star radius using more recent reddening maps
and angular diameter-color relations to $R_*=(10.3 \pm 1.9) R_\odot$. K and
J-band adaptive optics images of the field taken at this epoch using the NIRC2
imager on the Keck telescope show that the source and lens are still blended,
consistent with our light-curve model. With no statistically significant excess
flux detection we constrain the mass, $M_L= 0.24^{+0.28}_{-0.12}M_\odot$, and
distance, $D_L = 7.0 \pm 1.0$ kpc, of the lensing system. This supports the
interpretation of this event being a stellar binary in the galactic bulge. This
lens mass gives a companion mass of $M=0.07^{+0.08}_{-0.04}M_\odot$, close to
the boundary between being a star and a brown dwarf.
