Catalogue entry no. 627a by Max Loehr:
627 Pair of Bird Figures
Translucent light gray material with white speckles. The two bird figures, which are identical in shape and size, were obviously cut from the same pebble. Their design is uncommon and of peculiar hardness. No part harmonizes with any other, and some of the details, such as the eyes, the wavy crest, and horizontally fluted wings, or the striated appendage under the legs, are not paralleled among the conventional examples of bird figures. The raised-line technique used to define the various parts in distinctly reminiscent of Shang lapidary work, but the design as a whole, though harking back to Shang motifs, in incompatible with Shang originals. It would seem justifiable to classify these birds as archaistic items of uncertain, possibly recent date.