Thanks Jim, the info on engravings and the popularity of the gun in pigeon shooting is very interesting.
I have checked my gun once more but I am sad to say that I can't find any dating marks. On the other hand the barrels are indeed marked "Cañones Chromo-Niquel" and "-Bellota-", so that's a good thing.
I didn't know anything about spanish guns until I saw this gun at the gun store. Sure I had seen a couple of Aya no 2's but I never gave them much notice because my interest (until now) have laid solely on british side-by-side shotguns, and especially hammer guns. If someone had told me a few months ago that AyA and Merkel over/unders where fantastic, I would have shook my head and thought of him as an idiot. However, the looks, the balance and the quality of craftmanship this gun posesses hit me right in the face. I had to buy it, and now I am beginning to love it!
Merry Christmas!!