They are 39.5 mm and contain 23.3890 grams of pure silver.
First minted in 1741 in the early years of the reign of Empress Maria Therese, these beautiful silver coins were soon accepted around the world as legal tender for international trade. The empress died in 1780 and that date was made a permanent feature of the coin's design. The Maria Therese coin was originally minted in Austria. Virtually identical coins were later minted in England, Bohemia and France. Even into recent times these thalers (or talers) were regularly traded in North Africa and down the East African coast. I've had examples stamped with the chops of Chinese counting houses.
You may notice their size and resemblance to Spanish 8 reales. These, too, were often called thalers, eventually known by Britons and Americans as dollars, the ancestor of our silver dollars.
We have a few thalers that were minted some years ago. All are rated 833.3/1000 silver. I don't know how old they are, but I have had them for several years. All, as usual, are dated 1780. These are silver and have one of the most beautiful and intricate designs ever produced for coinage. They are 39.5 mm and contain 23.3890 grams of pure silver.