I've always been fascinated by the Spanish "Ruby" style pistols myself. The Eibar region of Spain was kind of like the "Khyber Pass" of its time, maybe better quality...
I looked at one 32 'Ruby' style blowback pistol similar to that one pictured above. It had strange grooves cut into the slide for gripping the slide to chamber a round...The grooves were square-cut (like a Channel-Lock pliers) and crescent shaped...I still can't quite figure out how they were cut in the slide...Seemed rather complex machining for what was probably a 'garage' shop...