What is the value of a 1797 two headed quarter?

It's not a real coin and it's not from 1797.

Two-headed (or tailed) coins are called "magician's coins". They're made by cutting two genuine coins in half using jeweler's tools and then swapping the sides. It's considered to be an altered or damaged item with no numismatic value.

However no US quarters were minted in 1797 and no modern State Quarters carry that date either, so it's probably not even made from a genuine US coin.