'64 half dollars are silver, worth probably $7 or more for the silver content. Mercury dimes are also silver, value probably starting around $1 each. Same for Roosevelt dimes if they're '64 or earlier.
Coins after '64 are not silver and generally worth face value.
I have sold several iphones on ebay, half of them to international buyers, and have never had a problem.Speaking of which, I have my wife's old 5s to list. I should do the same as you and get it up ASAP.