  We propose a general procedure for iterative inclusion of Stueckelberg fields
to convert the theory into gauge system being equivalent to the original one.
In so doing, we admit reducibility of the Stueckelberg gauge symmetry. In this
case, no pairing exists between Stueckelberg fields and gauge parameters,
unlike the irreducible Stueckelberg symmetry. The general procedure is
exemplified by the case of Proca model, with the third order involutive closure
chosen as the starting point. In this case, the set of Stueckelberg fields
includes, besides the scalar, also the second rank antisymmetric tensor. The
reducible Stueckelberg gauge symmetry is shown to admit different gauge fixing
conditions. One of the gauges reproduces the original Proca theory, while
another one excludes the original vector and the Stueckelberg scalar. In this
gauge, the irreducible massive spin one is represented by antisymmetric second
rank tensor obeying the third order field equations. Similar dual formulations
are expected to exist for the fields of various spins.
