Was king Offa of Mercia a Muslim?

Offa as a Muslim? The only evidence for this assertion is a copy of a
gold dinar, but Offa was on very good terms with the Pope, and he was
a strong supporter of Christian monasteries. Why should Offa issue a coin
that bore the inscription 'There is no God but Allah alone'? The theory
is: fraud. Offa's coin looked so much like the original dinar of the
Abbasid Dynasty that it made it easier for Mercia to trade with (Islamic)
Spain. The coin bore a wrongly-spelt Arabic inscription, plus a Latin
one: Offa Rex.

There is no evidence of Offa's supposed conversion to Islam. The coin on display in a British museum is not proof.

You've posted a link that actually answers your question, did you bother to read that information?!

offa was a Christian king

Of course he wasn't!

The source you linked to explains quite clearly that his having struck gold coins that were clumsily based on the Baghdadi dirham which was the only gold currency anyone in 8th-century Mercia would have ever seen, in no way suggests that he was even sympathetic to Islam, let alone a convert.

Here's a parallel case: the first coins ever made in Britain were struck for Celtic kings in the 1st century BCE; they were very debased copies of Greek coins that showed Alexander the Great in his chariot. This does not, obviously, mean that the Iron Age Celts were converts to Greek religion! They were just copying the first coins they had ever seen, brought to Britain by Greek traders. They probably had no idea who the guy in the chariot was supposed to be, in the same way that Offa and his workmen clearly could not read the Arabic inscription they copied.

No, he wasn't but so what? How does the fact that Offa wasn't a Muslim justify your obvious right-wing racist Nazi agenda?

All I know was that Offa was married to a lesbian.