Chinese Abacus. The abacus is first known in China from the Northern Song dynasty through the work of Shao Yong (1011-1077). Like many early inventions it is not clear precisely where it originally came from. Some say Central Asia; some Asia Minor and others China.
Snag(noun) a stump or base of a branch that has been lopped off; a short branch, or a sharp or rough branch; a knot; a protuberance. Snag(noun) a tooth projecting beyond the rest; contemptuously, a broken or decayed tooth.
1 tree ring - Any of the concentric rings of the cross-section of a tree trunk, representing a year's growth, or the layer of wood produced by a year's growth in a woody plant; also called annual ring.  snag - Literally first meant a stump on a tree trunk or a piece of timber underwater that obstructed navigation.