Bore diameter is .729 in both barrels. Gun is advertised as in an "unshot/unused condition."

Personally I think it was just a case of the barrels not being measured while striking as Mal said. If the gun is in unused condition, and it does look that way from the pictures I have seen, and bores are both .729 - then perhaps the barrels just were not measured when striking. Why else would one barrel measure 22 thou. and the other one 28 thou.?