Pre-1820 George prince of Wales was the Prince regent due to GIII's mental illness. Until his death coins were always struck in GIII's name.
However GIV before he became king had coins struck styling him as prince regent, he was the regent to Karl II too by way of him already being PR to his Fathers possessions.
So here are my examples as far as I know these are the only coins of the British royals to Carry the style prince regent.


There are many varieties of legend to the Pfenning even before he became GIV. Including GEORG T. N (George Tutor of)


GEORG D.G. T.N (inc die gratia)
And GEORG P. R. T. N
(Inc Prince Regent)
And then there are the issues of 1820 on where he styled himself King.


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https://en.numista.com/catalogue/pieces67728.html