Apsaros at latitude 41.6° (lat/lon 41.573, 41.573) is at the easternmost point on the Black Sea. It had a Roman fort at that location and was the furthest east the Empire extended at that time.
The Seven Sages mosaic with lines drawn at 41.6 degrees latitude from the left and right that intersect with lines projected from the sundial.
Pliny the Elder wrote of the Apsaros fortress in his book on Natural History. It is a possibility that he was responsible for creating the Seven Sages mosaic which is the stimulus for these inquiries. He was a wealthy man, a prolific author and as knowledgeable as any Roman of geography at that time.
The Seven Sages mosaic has an astonishing number of multiple overlaps of key points in not just this location but at several other important sites.