The ceiniog (la|denarius; en|penny; plural: ceiniogau; prob. from, "circle") was the basic currency of the medieval Welsh kingdoms such as Gwynedd and Deheubarth. Hywel Dda was the only ruler recorded as minting his own proper coins; however, the ceiniog was not a coin but a value of silver. The "legal penny" (la|denarius legalis; cy|ceiniog cyfreith) was the weight of 32 wheat grains in silver; the "curt penny" (cy|ceiniog cwta), the weight of 24 wheat grains. The latter was based on the old Roman pound; the former, Charlemagne's and Offa's.[1] The Welsh half-penny was the dymey of 12 wheat grains (roughly ⅓ the "legal penny")[2] and the farthing (quarter-penny) was the firdlyc of 6.[3]
Since the value in ceiniogau of most common goods and animals were regulated by the Laws of Hywel Dda, the system also simplified barter in Wales.