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 andanalysed together with the optical data. Over the past ten years this blazarhas exhibited enhanced activity. There is only weak correlation between radioand optical flares delays, usually protracted on longer timescales in the radiowith respect to the optical. In some cases no radio flare counterpart wasobserved for the optical outbursts. The radio variability, characterised bypeaks superposition, shows hints of some characteristic timescales (around the3-4 years), and a fluctuation mode between the flickering and the shot noise.The reconstructed spectral energy distribution, poorly monitored at highenergies, is preliminarily parameterised with a synchrotron-self Comptondescription. The smooth synchrotron continuum, peaked in the near-IR-opticalbands, strengthens the hypothesis that this source could be an intermediateblazar. Moreover the intense flux in millimetre bands, and the optical andX-ray brightness, might suggest a possible detectable gamma-ray emission.
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