This is a shrine (zushi) for a set of the Great Perfection of Wisdom Sutra (Skt. Mahāprajñāpāramitā-sūtra; Ch. Mohe bore boluomiduo jing; J. Daihannya kyō). Its six-hundred scrolls were divided between this and another shrine, three-hundred scrolls in each; the scrolls themselves are the principal object of worship enshrined within. The back of the shrine’s interior has the Sanskrit seed syllables (Skt. bīja; J. shuji) for the Buddhas Shaka (Skt. Śākyamuni) and Amida (Skt. Amitābha). The inner surfaces of the doors of both shrines, which come from Shinkōin Temple in Kyoto, feature paintings of the Sixteen Protective Deities who serve as the guardians of the enshrined sutra.
 
MIMOTO ShusakuEnglish by Mary Lewine 
Buddhist Art Paradise: Jewels of the Nara National Museum. Nara National Museum, 2021.7, p.339, no.138. 

This cylindrical feretory of the palace style is made of black lacquered wood. Its base consists of two layers of lotus seats: one seat is octagonal and consists of a double layer of petals, whereas the other seat has a single layer of sixteen petals. There is another lotus seat within the cylindrical feretory. Below the eaves of the roof, a lotus flower with eight petals is engraved as a decoration, and a hōju (magic jewel)-shaped ornament is attached at the top of the roof. It is conceivable that this feretory originally was one of a pair of feretories each of which had contained three hundred volumes of Daihannya-kyō (Mahāprajñyā sūtra). Its counterpart is now kept in the Cleveland Museum of Art in the United States of America. Four Buddhist deities are painted on each panel of the double-hinged doors, and thus originally sixteen deities were depicted, since one feretory has two double-hinged doors. Two disks are painted onto the back wall of the feretory, onto which Sanskrit symbols representing Shaka (Śākyamuni or Buddha) and Amida (Amitābha) are written. A canopy is engraved into the ceiling of the feretory. These decorations follow the style found on feretories for Buddhist statues. The images of sixteen deities painted on the doors are not included in the Besson-zakki a book on iconography. Judging from the exotic armor suits depicted in the images they probably follow the examples of Chinese icons during the Tang dynasty. The elegant and pleasant painting style of these deities is similar to the Buddhist paintings made during the late Heian and early Kamakura periods. 
Masterpieces of Nara National Museum. Nara National Museum, 1993, p.113, no.88.