franc

What's a private issue?

I recently looked in an old purse of mine and found a very strange British pound coin. It's dated 1984 and has the thistle and royal diadem design on the back. On the heads side there is a little star with a clear gem in the center. I immediately started searching the internet but I couldn't find any other coins like it or anyone who had heard of this. I thought it might be fake but it looks and feels legitimate and it would be odd for someone faking coins to put effort into making it stand out. Not being able to find any info at all on this coin is driving me crazy. Have any of you seen anything like this before? http://s24.photobucket.com/user/franc10/media/P1040140_zpsigkiop8j.jpg.html?sort=3&o=1 http://s24.photobucket.com/user/franc10/media/P1040135_zpsp1lnu4vd.jpg.html?sort=3&o=2 http://s24.photobucket.com/user/franc10/media/P1040132_zpsiclyuy9i.jpg.html?sort=3&o=3 http://s24.photobucket.com/user/franc10/media/P1040145_zps4it1j7pm.jpg.html?sort=3&o=0 EDIT: Could someone have had it modified for some reason? Have you heard of anyone doing that?