This class comprises instances of E2 Temporal Entity or E77 Persistent Item, i.e. items or phenomena that can be observed, either directly by human sensory impression, or enhanced with tools and measurement devices, such as physical things, their behavior, states and interactions or events. Conceptual objects can be present in events by their carriers such as books, digital media, or even human memory. By virtue of this presence, properties of conceptual objects, such as number of words can be observed on their carriers. If the respective properties between carriers differ, either they carry different instances of conceptual objects or the difference can be attributed to accidental deficiencies in one of the carriers. In that sense even immaterial objects are observable. By this model we give credit to the fact that frequently, the actually observed carriers of conceptual objects are not explicitly identified in documentation, i.e., the actual carrier is assumed having existed but is unknown as an individual.