Re-reading Mercian Hymns today, I looked for photos of Offa's coins on internet. A plethora of information and mis-information about Offa exists on-line. Here is a sampling:
BBC "Anglo Saxon Coins," (www.bbc.co.uk/history/trail).
British Museum, "Gold imitation dinar of Offa," (www.britishmuseum.org).
British Museum, "Silver Coin of Cynethryth, wife of Offa of Mercia,"(www.britishmuseum.org).
King Offa Primary School, "Who was King Offa?" (www.kingoffa.e-sussex.sch.uk).
Sheikh Abdullah Quilliam, "An Anglo-Saxon King Proclaims the Unity of Allah..."
"Coins of the Anglo-Saxon King Offa Rex" (www.cyberistan.org/islamic/offa.html).