  We evaluate gauge invariants (vacuum energy and gauge invariant overlap) for
numerical classical solutions in cubic open string field theory under
Asano-Kato's $a$-gauge fixing condition. We propose an efficient iterative
procedure for solving the equations of motion so that the BRST invariance of
the solutions is numerically ensured. The resulting gauge invariants are
numerically stable and almost equal to those of Schnabl's tachyon vacuum
solution in the well-defined region of a gauge parameter. These results provide
further evidence that the numerical and analytical solutions are gauge
equivalent.
