1. A solid ink stick comprising: an ink stick body formed of a phase change ink material, the ink stick body being configured for inclusion in a first set of ink sticks and having substantially a same size and shape as other ink sticks in the first set of ink sticks and the same size and shape as ink sticks in a second set of ink sticks, the first set of ink sticks being configured for insertion into a first model of printer that excludes the ink sticks of the second set of ink sticks and the second set of ink sticks being configured for insertion into a second model of printer that excludes the ink sticks of the first set of ink sticks; and an identification pattern formed on the ink stick body, the identification pattern being one identification pattern in a set of identification patterns, the identification pattern formed on the ink stick body being visually discernible from the other identification patterns in the set of identification patterns and configured with both protrusions and depressions in a surface of the ink stick body to differentiate the ink stick from the other ink sticks in the first set of ink sticks and to differentiate the ink stick from the ink sticks in the second set of ink sticks.