Commemorative coins are coins that were issued to commemorate some particular event or issue. Most world commemorative coins were issued from the 1960s onward, although there are numerous examples of commemorative coins of earlier date. Such coins have a distinct design with reference to the occasion on which they were issued. Many coins of this category serve as collectors items only, although some countries are also issuing commemorative coins for regular circulation. Vast numbers of thematic coins are continuously being issued, highlighting ancient monuments or sites, historical personalities, endangered species etc. While such thematic coins may or may not commemorate any particular event or jubilee, the distinction between commemorative coins and thematic coins is often blurred or ignored.