Mechanically, they are all straight blowback and lack a last-round holdopen feature or grip safety.One feature that can be tied to wartime service is the addition of a large rivet-looking knob on the left side of the slide.Some worked with Gabilondo, while many others negotiated their own deals directly with French purchasing agents.
In addition, a loophole in Spanish patent law gave these small shops an international advantage: a Spanish patent was only valid if the device in question was actually manufactured in Spain within three years of patent being granted.
The major arms designers of the time had their factories in France, Germany, Great Britain, and elsewhere, but not in Spain.
None of them shared interchangeable parts (or magazines), though, and each manufacturer used its own trademark name.
For the dedicated collector, these trade names make Eibar-type pistols a virtually bottomless well.
There are a few ways to determine if a particular one was made for French WWI contract (and thus likely saw military use).