Soroban with natural wood beads
The fact that this soroban has a closed back means that it is very likely to be an early variant of the 1-to-5 soroban. Its fifteen rods are made of metal and are somewhat corroded. All except the middle rod have a corresponding Kanji character on the horizontal bar. The construction of the frame with carefully mitred joints indicates that it is a so-called Banshu soroban.