After DIARM closed and was no longer available to make the Derby, American Arms contracted with Zabala Hermanos to make model Derby side lock shotguns.

When it comes to Spanish shotguns, model names have limited utility.

Over on Shotgun World there is a thread that concerns what appears to be an AyA model 53. The Aya model 53 is typically built as a medium game gun, but this one looks to have been made as a light game gun. Go Figure.