Seal; Signet

Concise Bible Dictionary:

Stones on which words, letters, or symbols are engraved. Anciently these were pierced, and by a cord or chain were hung from the arm or the neck, or they were set in rings and worn on the finger. The design was impressed on pieces of clay which were attached to official documents, which in the East are not considered authentic without being sealed (Ex. 28:1111With the work of an engraver in stone, like the engravings of a signet, shalt thou engrave the two stones with the names of the children of Israel: thou shalt make them to be set in ouches of gold. (Exodus 28:11); Esther 8:8,108Write ye also for the Jews, as it liketh you, in the king's name, and seal it with the king's ring: for the writing which is written in the king's name, and sealed with the king's ring, may no man reverse. (Esther 8:8)
10And he wrote in the king Ahasuerus' name, and sealed it with the king's ring, and sent letters by posts on horseback, and riders on mules, camels, and young dromedaries: (Esther 8:10)
; Job 38:1414It is turned as clay to the seal; and they stand as a garment. (Job 38:14); Dan. 6:1717And a stone was brought, and laid upon the mouth of the den; and the king sealed it with his own signet, and with the signet of his lords; that the purpose might not be changed concerning Daniel. (Daniel 6:17)). The seal was also used to ensure security, or to preserve the sanctity of things not to be revealed (Isa. 29:1111And the vision of all is become unto you as the words of a book that is sealed, which men deliver to one that is learned, saying, Read this, I pray thee: and he saith, I cannot; for it is sealed: (Isaiah 29:11); Dan. 12:4,94But thou, O Daniel, shut up the words, and seal the book, even to the time of the end: many shall run to and fro, and knowledge shall be increased. (Daniel 12:4)
9And he said, Go thy way, Daniel: for the words are closed up and sealed till the time of the end. (Daniel 12:9)
; Matt. 27:6666So they went, and made the sepulchre sure, sealing the stone, and setting a watch. (Matthew 27:66); Rev. 20:33And cast him into the bottomless pit, and shut him up, and set a seal upon him, that he should deceive the nations no more, till the thousand years should be fulfilled: and after that he must be loosed a little season. (Revelation 20:3); Rev. 22:1010And he saith unto me, Seal not the sayings of the prophecy of this book: for the time is at hand. (Revelation 22:10)).
A covenant was sealed by Nehemiah and those with him (Neh. 10:11Now those that sealed were, Nehemiah, the Tirshatha, the son of Hachaliah, and Zidkijah, (Nehemiah 10:1)). The believer, in crediting what God says of man, and of God’s salvation, virtually attaches his seal (vouches for the fact) that God is true (John 3:3333He that hath received his testimony hath set to his seal that God is true. (John 3:33)). “The foundation of God standeth sure, having this seal, The Lord knoweth them that are His [God’s side]; and, Let everyone that nameth the name of the Lord depart from iniquity [man’s side]” (2 Tim. 2:1919Nevertheless the foundation of God standeth sure, having this seal, The Lord knoweth them that are his. And, Let every one that nameth the name of Christ depart from iniquity. (2 Timothy 2:19)). This is an illustration of a double-seal turning on a pivot, of which either side could be used.
The roll in Revelation 5 had seven seals, so arranged that by breaking one seal a certain portion could be unrolled; and each seal was broken in succession until the whole was revealed.

“323. Seals” From Manners and Customs of the Bible:

The seal is, in the East, of more importance than the signature, and indeed is often used in place of a signature. No document is of any validity without it. The ordinary mode of using it is to cover it with ink, and press it on the paper. The seal is often connected with a ring, and worn on the finger. See note on Genesis 41:4242And Pharaoh took off his ring from his hand, and put it upon Joseph's hand, and arrayed him in vestures of fine linen, and put a gold chain about his neck; (Genesis 41:42) (#79).
Ancient seals have been found of various shapes—cylindrical, square, pyramidal, oval, and round. A very common style of seal among the ancient Egyptians was one made of stone, rounded on one side and flat on the other. The inscription for the seal was on the flat surface, and the convex surface was skillfully wrought into the form of a scarabaeus or beetle.
Since the beetle was worshiped by the Egyptians, whose example was followed by the Phenicians, after whose deities Ahab had gone, some have thought that Ahab’s seal was of this description.
Seals that were not set in rings were perforated with a hole through which a string passed, by means of which the seal was suspended from the neck. It is supposed that Judah’s was worn in this way (Gen. 38:1818And he said, What pledge shall I give thee? And she said, Thy signet, and thy bracelets, and thy staff that is in thine hand. And he gave it her, and came in unto her, and she conceived by him. (Genesis 38:18)).
Many ancient seals were in shape of a cylinder, and some of these were set in a frame which enabled the seal to revolve as the impression was made. Some beautiful specimens of this kind of seal have been found among the ruins in Chaldea and Assyria. The figures engraved on seals were various. Modern Oriental seals have usually the name of the owner on them, and often a sentence from the Koran. The ancient seals had devices of symbolical meaning, and letters either hieroglyphic or cuneiform.

“420. Impressions of Seals” From Manners and Customs of the Bible:

The bricks of Egypt, Babylonia, and Assyria boar marks which have evidently been made with a seal. Egyptian wine jars and mummy pits were sometimes sealed with clay. There have been found in Assyria public documents made of clay, and having the letters stamped in them, and the marks of official sealing. In the East, doors of granaries or of treasure rooms are to this day sometimes sealed with clay, so that it is impossible to enter without first breaking the seal. The sepulcher of Christ was probably sealed in this way. See note on Matthew 27:6666So they went, and made the sepulchre sure, sealing the stone, and setting a watch. (Matthew 27:66) (#735). Clay is used in preference to wax because the former hardens with the heat, while the latter melts. The engraving represents a lump of clay from Assyria, having several impressions of seals upon it.