  In this paper we conduct a careful multicanonical simulation of the isotropic
$3d$ plaquette ("gonihedric") Ising model and confirm that a planar, fuki-nuke
type order characterises the low-temperature phase of the model. From
consideration of the anisotropic limit of the model we define a class of order
parameters which can distinguish the low- and high-temperature phases in both
the anisotropic and isotropic cases. We also verify the recently voiced
suspicion that the order parameter like behaviour of the standard magnetic
susceptibility $\chi_m$ seen in previous Metropolis simulations was an artefact
of the algorithm failing to explore the phase space of the macroscopically
degenerate low-temperature phase. $\chi_m$ is therefore not a suitable order
parameter for the model.
