  We report the observation of the universal distribution of transparencies,
predicted by Schep and Bauer [Phys. Rev. Lett. {\bf 78}, 3015 (1997)] for dirty
sharp interfaces, in uniform Nb/AlO$_x$/Nb junctions with high specific
conductance ($10^8$ Ohm$^{-1}$cm$^{-2}$). Experiments used the BCS density of
states in superconducting niobium for transparency distribution probing.
Experimental results for both the dc $I-V$ curves at magnetic-field-suppressed
supercurrent and the Josephson critical current in zero magnetic field coincide
remarkably well with calculations based on the multimode theory of multiple
Andreev reflections and the Schep-Bauer distribution.
