How thick are a nickel and a dime? Action height question.

I have never seen a nickel or a dime, sorry. I need to fix the action on this cheap offshore dulcimer (in my profile pic atm.) but I don’t know what heights to use at the frets or even if nickels and dimes have varied in thickness over the years like our fake currency in England. 😇

I have some needle files in the mail, since it seems one of my (now adult) kids have swanned off with the ones from my toolkit, then I’ll be ready to fix it.

I am planning to stick to basics to start with but admire the playing of both Jessica Comeau and Stephen Seifert. I just love the unique sound of this beautiful instrument.

Hope someone can help me. Equivalent width UK coinage would suffice. 👍💚