When I form a corporation for a client, I purchase a customized corporate records book, which comes with share certificates and a corporate seal. This post explains what a corporate seal is and when it might be used.
A corporate seal is a hand-operated metal device that can emboss the corporation’s name and state and date of incorporation on a piece of paper. It, thus, can serve as evidence that the corporation acknowledges an agreement or other document as binding the corporation.
As an analogy, think of an English king, centuries ago, sealing a letter with molten wax and making an impression of his ring in the wax before it hardens. Whoever received the letter would know that it came from the king.