Let X, X be two locally finite, preordered sets and let R be any indecomposable commutative ring. The incidence algebra I(X, R), in a sense, represents X, because of the wellknown result that if the rings I(X, R) and I(X ,R) are isomorphic, then X and X are isomorphic. In this paper, we consider a preordered set X that need not be locally finite but has the property that each of its equivalence classes of equivalent elements is finite. Define