The "Astra" trademark belongs to the "Societa Unceta and compania" company (current name Astra-Unceta y Cia), located in the Guernica, Spain. Astra mod.600 appeared in 1943, being chambered for 9mm Luger cartridge only and also having shorter barrel and slide, than mod.400. This model also had been used by Wehrmacht (German army) and exported across the world.
Technically, the mod.600 is a blowback operated, hammer fired, single action semiautomatic pistol. It was chambered for 9x19mm Luger/parabellum cartridge.
The recoil spring is located around the barrel. The gun featured no manual safeties. One automatic safety is located at the rear of the grip and locks sear when gun does not gripped by the shooter properly; another, internal safety, disconets the trigger bar from the sear when gun is off the battery (slide does not closed completely). The slide stop is located at the left side of the frame.
Thanks to the long barrel and heavy weight, the gun was comfortable to fire and showed good acuuracy despite the fact that the blowback operated action is often assumed as unsuitable for full-powered ammunition such as 9mm Largo or 9mm Luger.