  A geometric study of twin and grain boundaries in crystals and quasicrystals
is achieved via coincidence site lattices (CSLs) and coincidence site modules
(CSMs), respectively. Recently, coincidences of shifted lattices and
multilattices (i.e. finite unions of shifted copies of a lattice) have been
investigated. Here, we solve the coincidence problem for a shifted hexagonal
lattice. This result allows us to analyze the coincidence isometries of the
hexagonal packing by viewing the hexagonal packing as a multilattice.
