  This note characterizes a universal Kripke frame for the variable-free
fragment of the reflection calculus with conservativity operators RC$^\nabla$.
The frame here is obtained from the set of all filters on the Ignatiev
RC$^\nabla$-algebra which is an isomorphic presentation of the
Lindenbaum--Tarski algebra of the variable-free fragment of RC$^\nabla$. We
give a constructive `coordinatewise' characterization of the set of filters and
of the frame relations corresponding to the modalities of the algebra.
