Big Mother Silver Coin, named "Maria-Tracy Taylor Silver Coin", is the main silver coin cast by Maria-Tracy, Queen of Habsburg Dynasty of Austria-Hungary in the18th century. Very rare in the early years, the old version of19th century and the cast version after 20th century are more common in the market. The weight of coins is kept between 27 and 28 grams, and that of silver is between 50% and 80%. Therefore, silver coin is a large and exquisite coin, which has been a trade silver coin in Europe, the Middle East, Africa and India for a long time. From the18th century to the 1970s and 1980s, a large number of over one billion pieces were cast, which almost became the trading currency of the whole Middle East and East Africa. Until modern times, some tribal areas in the Middle East were still negotiable precious metal currencies. Moreover, European countries issue a certain number of recast 1780 versions of big wet nurses every year for collection and sale. For more than 200 years, the big wet nurse's silver coins have been cast in huge quantities, with many versions, big and small, weak lace and bright lace. Austria, Hungary, Italy, France, the Netherlands, Germany, Britain, North Africa, East Africa, Yemen, Oman, Saudi Arabia, Ethiopia and India all have a large number of countries, with an unprecedented number of countries. In the market, most plates were cast in the middle and late last century. On the contrary, few genuine discs were cast before 1780, and the market price was high. In addition, it needs to be pointed out that many so-called pseudo-experts in China always think that a big wet nurse with the same mildew injury is wrong, which is wrong. For example, mommy's post-coinage molds are modeled after the previous molds, and most of them are no longer circulating local currency. Many copied molds are defective in themselves, because they are not circulating coins and are not valued by the mint, and usually a damaged coin mold is mass-produced, resulting in many cast plates having the same mold damage. This is normal in itself. We can't look at this post-casting foreign currency from the perspective of Chinese silver coins.