Ask an Antiques Question, Get an Answer ASAP!
I regret to say that there is virtually no chance of your coin having any precious metal content. Clearly the colour of the surround suggests gold. If it were gold then the 'hanger' at the top would be marker 375 or 9ct. I am sure that it will not be.
Secondly, I note that the ring at the top is not soldered (closed). If gold then it generally would be soldered together.
If you do a search under 'enamelled Queen Elizabeth coins' I believe that you will find other examples and people do ask more than £20 for them. Such a figure is I think optimistic though.
As a final check, next time you are in a high street, just pop into a jewellers. They will make sure whether there is any gold content. If there is not (and that's what I think) then you can be absolutely certain. Sorry .
A coin of your size in 22ct gold would probably be worth £200/300 but not many people would ruin it by applying colours and then enamelling or mounting in plastic. Best wishes. Greg