The following description was prepared by William Gross:
Breastplates – ornamental metal plates or shields hung in front of the Torah scroll – are found in all Ashkenazi communities, as well as Italy and Turkey, but designed differently in each community. In most cases, the breastplate is made of silver or silver-plated metal. In Italy, the breastplate is shaped like a half-coronet and known as the Chatzi-keter, "half-crown." In Turkey, the breastplate is called a Tas and assumes a variety of shapes – circular, triangular, oval, or even the Star of David. In Western, Central, and Eastern Europe the breastplate is called either Tas or Tziz; its function there is not merely ornamental: it designates which Torah scroll is to be used for the Torah reading on any particular occasion, with interchangeable plaques.
The most notable early breastplates, from 17th-century Germany and Holland, were either square or rectangular, but over time they became rounded and decorative, and bells or small dedicatory plaques were suspended from its lower edge. During this period, the design of breastplates was influenced by that of the Torah Ark and the parokhet (curtain) concealing it, featuring various architectural motifs, the menorah (the seven-branched candelabrum), Moses and Aaron, lions, or Torah crowns.
This round silver Tas for the Torah Scroll carries a very early date for silver from the Ottoman Empire. The use of the Shiviti formula and amuletic words makes it unusual as well. The use of the Torah Shield in the Ottoman Empire derives from the substantial European influence during the 19th century. There are additional Kabbalistic "names" including several of the names of God. This suggests that the text was really copied from a Shiviti on which such "names" are an integral part. The gilt round knob in the center might also represent an eye, which is itself an antidote to the evil eye. Inscription: I have set the Lord always before me (Psalms 16:8) Shadai Tzevaot (The eight-letter name of God) Donated to the Holy Community of Tokat (a quarter of Istanbul), May He build his city, Amen, the congregant, the honorable Rabbi Avraham Mizrachi, May the Lord sustain him and grant him favor, and May the Merciful One protect him and bless him, the year 5608 , according to the major reckoning