Is Pharaoh's head (from the Sphinx) primary source?

In the study of history as an academic discipline, a primary source (also called original source or evidence) is an artifact, a document, diary, manuscript, autobiography, a recording, or any other source of information that was created at the time under study.
Primary source - Wikipedia
en.wikipedia.org/wiki/Primary_source

Nothing is known about when the sphinx was created or whether the head was modified later, so it is not a source at all. It is an artifact: just what you see and nothing more.

When we say "primary source" we mean we are not looking at somebody's opinion of what it means.