Looks like a 1948 Half Crown from Great Britian. KM#866. Composition is Copper-Nickel, 32.3 mm and in the neighborhood of 14 grams (maybe someone else has an exact weight.) MIntage 71,165,000 and as for grade... I am not good enough yet. It's valued in the 2009 Krause at between $0.25 (F) and $1.00 (XF.) I love Crowns & Half Crowns.