Jim Haynes post above is exactly right! Both AyA and Ugartechea can and do make exquisite doubles on special order, both companies make these in both S x S and O/U configurations, although you seldom see the special order top line mopdels in The United States. About the best that is "routinely" seen in the US is the M53 or M56 AyA S x S guns, and their Merkel 203 clones, and these are not their best. About the best Ugartechea guns routinely seen here are several of the mid grade sidelock S x S guns being sold today as their "best" guns, but they also are nowhere their "best" efforts. I currently have an AyA M53 20 gauge, which is an excellent gun but not AyA's "best," and a Pair of Ugartechea true "best" gun sidelock O/U's in 12 and 20 gauges that are outstanding in every way. The commonly imported and encountered varieties of both makers are generally good values. Both these makers have been in business well over 75 years, they can certainly compete in most any market.
