Opium Weights is a fancy name for an ancient weight system
which has been used in Burma, Thailand, Laos, Cambodia and south China (Yunnan Province). The usage of this weight system can be tracked back to before the 12'Th century, and officially stopped when the British banned it in late 19'th century.The weights occur mostly in shape of beast and bird weights and were made using the lost wax method. Besides the beast and bird weights, which can be dated in a chronological system, special weights sculptured to resemble fish, horse, elephant, cow, rat, tiger, garuda, turtle, spider, naga, deer and other animals and even humans have been made. The weights was used weighing all kinds of commodities, smaller weights for expensive goods (opium, gems, gold, silver, ambergris etc.), bigger weights for inexpensive commodities (vegetables, fruits, hides etc.).The weights weigh from about 2 grams (1/8 of a tical) to 16 kilograms (10 viss), however most weights are found in the range from 80 grams to 320 grams. The smaller and the bigger weights are rarer. Age adds to the rarity of the weights too, the older the rarer.
Much more can be read in:
From Earth to Heaven, By Donald and Joan Gear 1992, Roadstar, 1992.