S925 Silver Double-sided Vajra Nine Palace Tag

Two systems on one plaque: nine-grid on one face, vajra on the other. The nine-grid plaque in Tibet was originally a tool for working out directions and choosing days. The face carries a three-by-three grid with the numbers one to nine in the order of the Luo Shu, an outer ring of eight trigrams, and often a further ring of twelve zodiac animals. Later it became a plaque to carry, and the symbols stayed while the calculations may no longer be used. The vajra is a ritual implement. With two faces, one looks out and one lies against the chest, and the wearer decides which is which.

A double-sided plaque needs thickness. Both faces carry pattern, and during die casting the silver flows through the mould; too thin, and the two faces compete for metal. The front comes out crisp and the back muddled, or the back shows through as a ghost on the front. The edge usually takes a ring of beads or a plain border, which separates the two faces and keeps the corners from chipping. The beads of a beaded border must be uniform; one small and the whole ring shows it. A plain border has the advantage of not trapping dust, which collects in the gaps of beading.

The numbers of the nine-grid are not filled in at random. One sits north and nine south, and the three numbers in any row, column or diagonal add to fifteen, which is the basic square of the Luo Shu. Tibetan nine-grid plaques add colours and directions to the numbers, and the details differ from region to region. When buying this kind of plaque, check that the numbers are in the right places rather than whether the pattern is pretty. Numbers in the wrong places and the finest pattern is still a misprint.

A flat plaque lies against the chest and doesn't swing the way a three-dimensional pendant does, so it doesn't push a point out through a shirt. The advantage of two faces is that turning it over gives a different reading; worn long enough, swapping sides is like swapping pieces. The cord passes through the hole at the top, and that hole should be rounded over, because a square hole with straight edges wears a cord fastest. The plaque has weight, so the chain must be able to carry it; a fine chain on a heavy plaque and the chain is what breaks. Check the clasp too: a spring ring holds better than a lobster claw on a heavy piece.

Flat silver shows scratches more than anything else. A pocket shared with keys and it comes out with white lines across the face. The oxidised black sits in the lettering and in the shadow of the pattern. Don't wipe the whole face, because flatten the contrast and the nine-grid becomes a blank plate. Don't stack the plaque against hard objects; pad it with soft cloth or give it a small bag of its own. Carrying it out, use an inner pocket rather than an outer one, which also holds a phone and keys. Face the plaque inward, against cloth, so the back takes the wear.