  We present new X-ray, radio, and optical data for the unusual galaxy/cluster
system J2310-437. Our results confirm the presence of an active nucleus, and
suggest an interpretation as an anomalous BL Lac object of bulk relativistic
Doppler factor < 2, with an optically deficient radio-to-X-ray spectrum. The
radio, optical, and soft X-ray flux densities could lie along a single
power-law function, lacking the curvature typical of BL Lac objects. Compared
with other known sources that may have comparable multifrequency spectra,
J2310-437 is the most extreme. Its low isotropic optical/UV radiation is
consistent with the intensity of external photons governing the electron
spectral break through Compton cooling; in this source the external photon
density would be too low to produce a spectral break below the X-ray.
