Unless the gun was bought in Europe, there should be an importer's name on it. Depending on the age, it might be KBI, Tristar, American Arms or Galef.
If a web search doesn't find the importer, let me know and I will see if I can find an address if the company is still in business.
The Zabala guns are pretty good quality as Spanish shotguns go, and they have been imported under several names, including Charles Daly.
Jim