Enna was a small German lens house in Munich which made some sterling designs; many of their lenses were sold in the US under the Sandmar brand.

Enna Werk is still in business, but moved their operations to Wegscheid on the Austrian border some years ago. There they built a state-of-the-art new factory dedicated to precision tool making and plastic injection molding. In the town they own a big old building which was formerly a schoolhouse, and the optical works were moved there. Their main products today are Plastic Injection Moulds.

The reason for the move was that the original factory in Munich had become too valuable as real estate and workers in Munich were paid much higher wages than at Wegscheid, which is a rural area. The current owner is Dr. Werner Appelt, a medical doctor who was forced to take over management of the company when his father, the founder, died. With his mother's death in the late 80s he came into full ownership. The chief optical designer for Enna was Dr. Siegfried  Schafer who deserves to be better known in the history of optics.

He designed one of the first commercially sold zoom lenses, and invented the idea of making one lens barrel which could accept a variety of mounts on the rear and provide auto diaphragm operation. These were sold as Enna socket-mount lenses.He was always an avid photographer and user of his own designs. Some of his last projects before retiring were the optical system for the Gossen spot meter, which was built by Enna, and some aspherical moulds for contact lenses. Enna made lens elements and complete lenses for major German optical houses on an OEM basis. The only known history is . The name, Enna, is the founder's daughter's name reversed

Further Reading :

Enna Taschen Buch_ by Friedrich-W. Voigt, published by Heering in 1964
Wright and Wilkinson's LENS COLLECTORS VADE MECUM