"From our vantage point, Mercury and Venus, called inferior planets because their orbits lie between the earth and the sun, appear to oscillate back and forth relative to the sun over a short angular distance, as if attached to it by an invisible extendable cord. For the ancients they were the guardians of the sun, sometimes leading and other times following the great luminary. By constrast, the superior planets, Mars, Jupiter, and Saturn, possessing orbits outside that of the earth, advance all the way around the sky and occasionally can be seen opposite the sun." (Skywatchers)

Moon was recognized as the closest of the 'planets', but that meant measuring from the earth, not from the sun. In the picture above a part of the Moon is hidden behind the world mountain (drawn with 4 times 5 'fingers').

If we are certain that the two smaller circles below the Sun represent Venus and Mercury, then we will know that the bigger of them must be Venus and the smaller one (even closer to the Sun) must be Mercury.

The brilliance of Venus is divided in two parts by a dark broad string, presumably meaning that morning and evening star appearances are separated by 8 nights of invisibility. The dark broad string should represent the time when Venus is invisible.

From this we can infer that Mercury in the picture is drawn as the opposite of Venus. It has a central 'golden band' instead of a central dark string. This band divides the orbit of Mercury in two - either we will see him (?) in the morning or in the evening. But he is very hard to catch sight of, therefore his visibility has been drawn like 2 dark strings between which Sun is hiding him.