A keepsake marriage certificate is a decorative certificate meant for the purpose of decor. This is merely something that can be shown off to guests and is utilized as a conversation piece. It commemorates the wedding and is kept as a keepsake of your wedding day. These certificates are highly decorative and usually involve the formal seal of the place which sanctifies your union. This differs from a legal marriage document and cannot be used as proof of a marriage. A legal marriage certificate is one that is issued by your government authorities and documents your marriage legally. This document is usual signed by the officiant (though this varies by state).