American Arms imported side by side, side lock, Spanish shotguns they sold under the model name Derby from at least two different makers; Zabala Hermanos (ZH) and DIARM S.A. The ZH guns were so marked on barrel flats and water table. The DIARM guns were marked Sarriugarte on the top of the barrels and had the makers mark of Armas ERBI (usually BEST) on barrel flats and water table.

American Arms imported the DIARM guns first, and switched to the ZH guns when DIARM went out of business. The DIARM guns have a distinctive engraving pattern. The ZH guns had coil mainsprings and a distinctive arrangement of pins visible on the exterior of the locks. The ZH side plate engraving is roll marked, like that of the AyA # 2.

Here are examples of each from guns on Guns International:

ZH:

http://www.gunsinternational.com/guns-fo...un_id=100729790

http://www.gunsinternational.com/guns-fo...un_id=100671458

http://www.gunsinternational.com/guns-fo...un_id=100482215


DIARM:

http://www.gunsinternational.com/guns-fo...un_id=100716469

http://www.gunsinternational.com/guns-fo...un_id=100683117

http://www.gunsinternational.com/guns-fo...un_id=100653458

http://www.gunsinternational.com/guns-fo...un_id=100647162