  We demonstrate that the standard Stueckelberg-modified Proca theory (i.e. a
massive Abelian 1-form theory) respects the classical gauge and corresponding
quantum (anti-)BRST symmetry transformations in any arbitrary dimension of
spacetime within the framework of Becchi-Rouet-Stora-Tyutin (BRST) formalism.
We further show that the Stueckelberg formalism gets modified in the two
(1+1)-dimensions of spacetime due to a couple of discrete duality symmetries in
the theory which turn out to be responsible for the existence of the nilpotent
(anti-)co-BRST symmetry transformations corresponding to the nilpotent
(anti-)BRST symmetry transformations of our theory. These nilpotent symmetries
exist together in the modified version of the two (1+1)-dimensional (2D) Proca
theory. We provide the mathematical basis for the modification of the
Stueckelberg-technique, the existence of the discrete duality as well as the
continuous (anti-)co-BRST symmetry transformations in the 2D modified version
of Proca theory.
