The compositions of this sutra box’s surfaces were created by the technique of sōkin (“inlaid gold,” also known as chinkin). In this technique, a design is first etched into a lacquered surface and then gold is worked into the etched grooves. Minute shards of iridescent shell in a spectrum of colors are sprinkled into the borders surrounding the designs of each surface. Many similar works came from a studio in Hangzhou, China; perhaps this was produced in that area.
 
MIMOTO ShusakuEnglish by Mary Lewine 
Buddhist Art Paradise: Jewels of the Nara National Museum. Nara National Museum, 2021.7, p.346, no.62. 

The Sōkin method of decoration involves the steps of first engraving designs with a needle in a lacquered surface, then filling the carved lines with soft lacquer into which gold foil is inlaid. This method is also called by the name "Chinkin".
This sutra case is oblong and of the aikuchi type. The edges of the lid are planed off. The top of the lid is decorated with the design of phoenixes, the two longer sides of the case-body are decorated with a pair of peacocks, one short side is decorated with a pair of parrots, and the other short side is decorated with images of Bosatsu (Bodhisattva), which appear in the attire of monks and are surrounded by clouds. The designs are all precisely depicted in detail. Carved Chinese characters are on the upper part of the shorter side of the case and on the shorter side of the lid.
It is rare that Buddhist images are depicted on one side of a sutra case. Hardly any example of such sutra cases can be found, except for this case and another one kept in Daitoku-ji temple. The decorations with mother-of-pearl on the lid and on the rim of the case were probably added later. 
Masterpieces of Nara National Museum. Nara National Museum, 1993, p.112, no.87.