Himalayan Art Resources, item no. 24640.
Tsongkapa, Lobsang Drapa (1357-1419), was the founder of the Gelugpa School of Tibetan Buddhism. In 1409 he established the Ganden Monastery in Lhasa which became the principal seat of the school. The reverse of the thangka bears an image of a stupa and large, repeated inscriptions of the consecration mantra om ah hum, imbuing the body, speech and mind of the Buddha. The letters at the top of the stupa are abraded but appear to praise Tsongkhapa.