wrote

A Manx 50p note, you said? They had subunit banknotes? Interesting,
indeed.
The only other nation that I know of with subunits in bankotes was the
50-cent note in the Bahamas. I don't doubt, however, that there are other
places in the world with similar notes.

Bank of England 10 shilling notes were in regular use until 1970, when they
were superseded by the 50 pence coin. Smaller denomination Treasury notes
were printed during WW1, though not issued.

Peter