Thanks PP, I had come across some of this before, I cannot recall where, but whoever wrote the piece did not give as fulsome an expalanation as you have.
I still think the Marcan coin story is a good one ! quite clever, in it Jesus has to ask for a coin, suggesting his mendicant nature yes, but also that he would not choose to carry such a dirty idolatrous thing. And the "Pay Caesar's things to Caesar..... " line is good !
But the Writer of Mark was producing Fiction, not historical fact obviously. I do wonder what actual Coin he visualised in his mind, but any of the time would do it seems. If he wrote in Rome or vicinity he may have been thinking of a coin he was more familiar with perhaps.