In the 1880s, a New York envelope manufacturer invented the string and button envelope closure, which consists of two round disks riveted to the seal flap and body of the envelope. The envelope is closed by twisting a string attached to the flap button around the lower button, thus holding the contents under “tension.” The envelope was called the Tension Tie.

Postal regulations at the time did not permit third or fourth class mail to be sealed, making the Tension Tie envelope an immensely popular product. In fact, the company became so well known for this envelope, its name was changed to Tension Envelope Company.

In 1937, the Berkowitz Envelope Company acquired the assets and patents of Tension Envelope, and it became the fifth plant owned by the company. In 1944, the company’s plant and sales organization was united under the well-known Tension name as Tension Envelope Corporation. Back in the 1940s, the name Tension Envelope had already been recognized by the Brand Names Foundation for over 50 years. Tension Envelope is now a name recognized by financial institutions, photofinishers, direct marketers, utilities, insurance companies, and dozens of other industries as an innovative manufacturer of high-quality envelopes and one of the leading direct-to-user envelope companies in the country. The company now has plants located from coast to coast with 25 sales/service offices in major markets. The namesake Tension Tie envelope is still manufactured today, primarily for interoffice mail, packaging, and filing applications.