The nose in this example is a regular circle which required focused directed stonework. The mouth is rectangular with a 90 degree intersection of lines.
Cultural imperatives may have suggested the tool maker select this stone for a tool because of the unique fossil exposure which could make for easy decoration of the tool edge with a simple facial likeness.
The November 2014 discovery of a shell from Java which had been engraved by Homo erectus has changed some mainstream attitudes regarding the possibility of art behaviors by early humans who in some circles are still characterized as ape-like. Just like the shell in the British Museum, we can look to current collections of "tools" to explore the possibility of the artistic inclusion of images and icons in these very old artifacts.