What's the best coin to conduct heat

I was thinking pennies (copper) but now they aren't made of pure copper.. So what's the best: pennies, nickels, dimes, or quarters?

US dimes and quarters are made with an alloy that is 91.67% copper, the rest being nickel.
That is the highest proportion of copper of all current coins; so those would be the best heat conductors.

Well nickels get hot slower pennies get got faster and falso dimes