If the signs are certain kinds of plastic the permanent marker can sometimes embed ink the plastic. If you soak a piece of the sign in isopropyl and it swells then you likely have something the ink will soak into.

Some markers are more permanent than others I guess (I came across some that weren’t really bothered by isopropyl or solvent).

For speed I’d suggest a stencil and some nasty spray paint (the type that isn’t easily removed).

Or a dry erase marker if that's a billboard. Color over, erase.

It's a unit of currency.

Pence is the opposite of suspense

Pence was the vice president of the first term.

Two pence, or tuppence, is 2 pennies, so a pence must be one penny. A Trumpence is valueless, however.

How did you make the r and n almost completely overlap? Letter sorcery...