It not only shows the dead alien (probably from the Roswell crash) itself, but also the hanger and the alien body being carried into the hanger from the military ambulance that delivered it. It has enough clues to accurately date the footage from the late 1940s.
The editors describe the find as "monumentally interesting", indeed "authentic". The magazine has not disclosed how UNCENSORED discovered or was given the footage, but is adamant about its authenticity.
While UNCENSORED was the first magazine to publish stills from the clip, the complete footage itself was not released on the internet by the magazine until now.