The Turin-Milan Hours, a book of prayers and masses, contains images executed by multiple hands. One, known as Hand G, is often thought to be Jan van Eyck. Five miniatures – some scholars include two more – are attributed to Hand G. They show refined execution with delicate detail, rich color, light reflections, and atmospheric effects. Some contain heraldry that suggests ownership by Duke John of Bavaria, for whom Jan van Eyck worked in 1422–1424. Many scholars propose that Jan painted the miniatures before John’s death at the start of January 1425. They would then be the artist’s earliest known works.

However, information offered by the heraldry is inconclusive. Tiny, usually unnoticed armorials in the Birth of John the Baptist miniature are more likely to belong to the person who commissioned these images. Hand G’s compositions show motifs in common circulation, probably through model books that were standard workshop tools; Jan van Eyck’s certain works are more original. Some of Hand G’s images depend upon prototypes of the later 1440s or early 1450s by Rogier van der Weyden and Petrus Christus. In some miniatures, the subject matter is not clearly represented, and even misunderstood; we think of Jan van Eyck as understanding his subjects, however original some of them were. Moreover, the artistic quality varies in this group of miniatures.

It is concluded that the Jan van Eyck whom we know from his larger paintings is not Hand G. The latter was a talented artist, perhaps initially trained by Jan van Eyck, who worked with Hands F through K c. 1450, to paint unbound leaves bought by the young male patron seen in miniatures by other hands.