  About twenty years of radio observations in five bands (from 4.8 to 37 GHz)
of the BL Lac object GC 0109+224 (S2 0109+22, RGB J0112+227), are presented and
analysed together with the optical data. Over the past ten years this blazar
has exhibited enhanced activity. There is only weak correlation between radio
and optical flares delays, usually protracted on longer timescales in the radio
with respect to the optical. In some cases no radio flare counterpart was
observed for the optical outbursts. The radio variability, characterised by
peaks superposition, shows hints of some characteristic timescales (around the
3-4 years), and a fluctuation mode between the flickering and the shot noise.
The reconstructed spectral energy distribution, poorly monitored at high
energies, is preliminarily parameterised with a synchrotron-self Compton
description. The smooth synchrotron continuum, peaked in the near-IR-optical
bands, strengthens the hypothesis that this source could be an intermediate
blazar. Moreover the intense flux in millimetre bands, and the optical and
X-ray brightness, might suggest a possible detectable gamma-ray emission.
