Roger11
Very carefully, use a very small, pointed knife blade, and insert it into the small slot separating the two halves. You are going to pry OFF the half WITHOUT the lanyard attachment hole (so you are going to swing the TOP of the knife blade back TOWARDS the half WITH the lanyard attachment hole, because the half WITHOUT the lanyard attachment hole slides up, over and then locks down into the half WITH the attachment hole). It comes off very easily and can be done many times if you are careful.
Hope this helps.