  We quantize by the Dirac - Wheeler-DeWitt method the canonical formulation of
the Schwarzschild black hole developed in a previous paper. We investigate the
properties of the operators that generate rigid symmetries of the Hamiltonian,
establish the form of the invariant measure under the rigid transformations,
and determine the gauge fixed Hilbert space of states. We also prove that the
reduced quantization method leads to the same Hilbert space for a suitable
gauge fixing.
