Original Item: Only One Available. Well these are RARE!!! There isn't much information out there at all about the X51 helmets, which were developed and tested during the 1950s. They were seen as an attempt to use new technology to improve upon the M1 helmet, which had served the U.S. Military well during WWII. Also with the post-war budget cuts, they looked to create a "Universal Helmet", which would be able to meet the needs of all service members.

The X-51 was the second of these developed, and it had an aluminum outer shell, combined with liner made from nylon pressed together in securing resin. The liner was made extremely robust, enough so that it would be able to function as a tanker helmet by itself, as it had its own chin strap separate from the shell, as with the M1 Helmet.

The internal rigging was similar to the M1 Helmet, and in fact utilizes two M1 style sweatbands attached together to go around the head, with additional supports lower down. There is a crown pad as well, which indicates the size on this example to be SMALL.

Unfortunately, the helmet was never adopted, and the entire project was scrapped. Never put into production, examples of these helmets are extremely rare, whether it be the complete helmet, the shell, or just the liner, as we have here.

Very rare and a great addition to any U.S. military helmet collection!

More on the X51 Helmet Project:
Following the end of World War II the Army entered a period of massive demobilization and severe budget cuts. Most major helmet design projects, such as the T-19 and T-20 series, were scrapped with the cessation of hostilities. In 1949 a new design project was authorized to create a 'universal helmet' utilizing the scientific advancements of the World War II period. The theory behind the design was that one helmet could be utilized by infantry, airborne, and armor personnel thus eliminating all the various specialized helmets. The first of these 'universal' designs was the X-49 helmet which was followed by the X-51 helmet.

The helmets utilized a laminated nylon helmet liner which would be worn alone by armored personnel inside the tank. The liner was designed without a brim and cut high in the back to allow the tank crew to use the sighting devices without having to remove the liner. The helmet's aluminum shell was thought to be superior to the M-1 helmet because of it's light weight and superior ballistic properties when combined with the new liner. The X-49 almost immediately ran into problems because of de-lamination of the liner's nylon layers. Increasing the number of layers in the X-51 model seemed to correct this problem and the helmet was produced in a limited number for field tests and later, combat tests, in Korea.

Several problems were encountered in the field however, the lower sides of the X-51 interfered with hearing and the helmet silhouette was found to too closely resemble the Russian Ssh39 helmets sometimes used by the North Koreans. Additionally prolonged usage once again resulted in de-lamination of the nylon layers of the liner. The concept of a 'universal helmet' was abandoned following the failure of the X-51 design.