Unique ID: 53
Gallo Belgic Aa2, of GB-Aa2 for short, is the quarter stater that accompanied the GB-Aa staters. These were minted in stages between 175 BC and 125 BC. This coin is class 2b (of 6) so was minted around the start of this time range, possibly to help finance wars against the Germanic tribes.
Note that the rarity figure is based on the catalogue in “Gaulish and Early British Gold Coinage” by Dr. John Sills and is likely to be overstated.