Armas Ego (Florentino Arizaga) was in business from the early 1950's until just a few years ago. Like many of the Basque makers the company turned out a wide range of products, ranging from inexpensive boxlock shotguns to some rather nice double rifles. Armas Ego is generally thought of as a quality manufacturer, but not in the same league as Grulla, Garbi or Arrizabalaga. Because of the diversity of the products offered, each gun must be evaluated on its own merit. There is no inherent value in the name.
The question is, what have you got - a boxlock or a sidelock? The difference is explained here:
http://www.hallowellco.com/boxlock.htm
The question of value cannot be approached without knowing whether it is a sidelock or not. The age, however, should be easy to determine. The Spanish system of proof marks includes a date code. These codes can be seen in the table at the bottom of this page:
http://www.star-firearms.com/firearms/proof.shtml
Removing the barrels and examining the proof marks will tell you a lot about the gun - not just its age, but what loads it was meant to shoot, chamber length and even the barrel weight. Spanish proof marks are easy to research on the net.
Knowing the name of the model (if there was one) is not always helpful, but the model name was often engraved on the trigger tang. It is useful to know that the Basques look to fine English guns as their role model, primarily the sidelocks. Looking at the specific features of your gun and its engraving (if it is a sidelock), and comparing it to various models from Purdey or Holland & Holland will give you an idea of what the maker was trying to accomplish. If your gun is a boxlock, then its features will be less distinguishing - generic Anson & Deeley.
The presence of a pistol grip or beavertail fore end indicate a gun made for export to the American market. For internal consumption or the European market the classic English straight grip and splinter fore end was (and is) the norm.
A nice Basque gun is always a good find. Please let us know what you have, or better yet post a picture or two.
Sharptail