The images from the CT scanning are transverse section of the qin. With the use of OsiriX, a 3D model was generated (Video 2). The 3D multiplanar reformatting (MPR) viewer engine in OsiriX allowed us to view the qin's internal structure and the change in density of its surface and bottom boards. It could also render series of images in a range along any selected axis at a chosen interval and shading.
Video 2. 3D model of the qin.
Exploring with the 3D MPR viewer along the coronal plane of the qin’s surface board, at a level close to the hui (徽) (i.e. near to the exterior), two coins could be found around the neck region (Fig. 5). The two coins were at 2.31cm and 2.45cm in diameters respectively (Fig. 6). Coins from the ancient China were often casted with characters about the era they were made. However, the exploration of the density of the coins and the surface board could not clearly inform whether there were any characters on the coins. If the characters on the coins were recognized, the results would have provided some insights on the qin's history.
Fig. 5. Looking from the back of the qin, a coronal plane with two coins, at an axis close to hui (circular shapes along the right side of the qin in this figure).
Fig. 6. The diameters of the coins.
The two coins align with the filled hole (Fig. 7). The alignment raises the questions of whether the two coins were put to the surface board to fill two similar holes. Figs 4d and 4e show that the coins were covering two similar holes, like the one in Fig. 4f. While holes at the neck region of the surface board are not a structural design of a qin, why are there three holes on this qin? The top two holes are masked by coins and further concealed by a layer of lacquer. Why did the maker or the repairer(s) of this qin hide up the coins and their respective holes, but keep the third hole being seen? If researchers in the future can trace the stories and the rationales of the coins and the holes on the surface board, one of the gaps in the history of this qin will be filled.
Fig. 7. Coins align with the filled hole.