That threepence is a silver coin minted between 1927-1936 under King George V of Great Britain.That's him on the obverse and the reverse design is acorns and oak leaves.It's only worth about 50 cents in that condition because they made 6,252,000 of them.The siver content is only 50% though.
Roy,the reverse was designed by George Kruger-Gray.It was the obverse that was designed by Sir Bertram MacKennal. Here's an article about George Kruger-Gray; http://en.wikipedia.org/wiki/George_Kruger-Gray . Aidan.