The first Desert Eagles were manufactured in Israel and started appearing on gun dealers' shelves in the US around 1985. Given the fact that the IMI is best known for the Uzi series of submachine guns and the Galil rifles, it isn't surprising that the Desert Eagle departs radically from many other semiauto pistol designs, though the exterior belays this.
Internally things are different.
The gas system employs a fixed, shrouded barrel which stays in position on the frame during firing, with gas coming up a port just ahead of the chamber to operate a three-lug rotating bolt that rides in the slide assembly. The fixed barrel gives the gun a lot of potential accuracy, a potential realized with most of these pistols when fired with quality ammunition. The .50 AE uses a rebated cartridge head of 0.514 inch - the same dimension as the .44 Magnum rim. This made it practical to create a cartridge with a .50-caliber bullet without necessitating the production of a new slide assemble or bolt. All that's changed is the barrel and a few other odds and ends of parts.