  We construct a four dimensional chiral N=1 space-time supersymmetric
perturbative Type I vacuum corresponding to a compactification on a toroidal
Z_2 X Z_2 X Z_3 orbifold with a discrete Wilson line. This model is
non-perturbative from the heterotic viewpoint. It has three chiral families in
the SU(4)_c X SU(2)_w X U(1) subgroup of the total gauge group. We compute the
tree-level superpotential in this model. There appears to be no obvious
obstruction to Higgs the gauge group down to SU(3)_c X SU(2)_w X U(1)_Y and
obtain the Standard Model gauge group with three chiral families.
