  Local M-operators for the classical sine-Gordon model in discrete space-time
are constructed by convolution of the quantum trigonometric 4$\times$4 R-matrix
with certain vectors in its "quantum" space. Components of the vectors are
identified with $\tau$-functions of the model. This construction generalizes
the known representation of M-operators in continuous time models in terms of
Lax operators and classical $r$-matrix.
