Collectible coins encompass a wide range of numismatic items, including historical pieces, commemorative coins, and error coins. The United States "So-Called Dollars" refer specifically to a category of medals and tokens that were issued to commemorate events or significant figures, often resembling dollar coins. The Hibler-Kappen reference pertains to a catalog that organizes these items, particularly focusing on issues from the late 19th and early 20th centuries. The year 1904 marks the issuance of several notable So-Called Dollars, which are sought after by collectors for their historical and aesthetic value.