I have a chance to buy an over and under 12 gauge which I'm stumped about. Made in Gardeno Italy, it is marked on one side of the receiver "Castellani", and on the other side it looks like "Star Lega", or "Star Vega".
What is this shotgun's value? What is it designed for (trap, skeet, hunting)? Any guess on how old it may be?
Thanks for any help you can give.

I spent a good bit of time trying to find something out and about all I now know is you spelled Gardeno wrong, its Gardone.
Your best bet is to study the gun in hand, very closely. Is it made with quality, with care? Are the parts well finished, the operation smooth and flawless? If there are tool marks, sloppy or stiff operation or simply evidence of inattention to detail, it's probably worth $200-400, condition withstanding. If it looks like a Cadalac, $800-1,000+. Superior workmanship throughout, highly engraved (real engraving, not etching), gold or silver and wood that looks superior, it could be a "best gun" and worth $1,000's. (Doubt if its the last... such a maker would be proud enough to put his name on it.)

Mind you, this is all way out speculation on my part.

Bruno Castellani was a maker of shotguns in Italy. I don't think they still make guns. If you do a google search you will find a few used listed at pretty high prices. As such they are probably a well made shotgun. Parts if needed would be a problem from what I could find.

I have two Castellani shotguns. One is an over/under. It is a "Jupiter". It has two barrels. One is a single barrel with an elevated sight rib for shooting trap and the other is a double barreled field set up. Both set ups are 31inches in length with tight/full chokes.

The other Castellani is a three-barreled 12ga. Oh yeah, both are chambered for 12ga. If you email me I'll send you pics. I too am looking for information that might tell me the value. I use both shotguns in the field and they're both fun to shoot.