Offered here is a 1918 Lincoln Commemorative Half Dollar. It is graded by CAC as MS-63. The coin in the above pictures is the one you will receive. 1918 Illinois Centennial Lincoln Half Dollar. Illinois Centennial Half Dollar Coin Specifications. Morgan (obverse), John R. Sinnock (reverse) Composition: 90% silver, 10% copper Weight: 12.50 grams Diameter: 30.6 mm Authorization: Public Law 65-163 Maximum Authorized Mintage: 100,000. Illinois Centennial Half Dollar Mintage.