Thanks Nomercy448 - it looks like you got me on the right track. Did some googling on Arizmendi and other Spanish makers and I found an Isidro Gaztanaga a Eibar "Destroyer" with the exact 3 stampings at the back of the frame. The one I have is different in that it has none of the patent or name markings in the slide like most everything I saw on-line has, but it definitely appears to be from the Eibar region and it breaks down exactly like a Arizmendi model I watched being stripped on YouTube.