Andrew Bayne knew this coin was a Charles I Scottish twenty pence piece but he wanted to know what it might be worth. Lots of Scottish coins are found in England and the examples that turn up most frequently are pennies of Alexander III and twenty pence pieces of Charles I.
There are many different varieties of this coin but due to its overall condition I can’t pin this one down to a specific reference number in Cons of Scotland, Ireland and the Islands.
The coin would grade only Fair and it is buckled and scratched, especially on the obverse. It’s not a rare coin and in its present condition it would be worth £10 at best.