Check the receiver and barrel
No published sn data. 10-200 USD
Your rifle is likely chambered in 6.5x52 Carcano. This can be veried by a gunsmith.
Depending on condition and originality (no modifications) and assuming the rifle is a 6.5mm Carcano, about $150.
arund 450,000 or so, depending on calibre
Unfortunately, we have no idea what rifle you have. Gardone Val Trompia is a town in Italy. It is not a make/ model of a gun. It is possible that you have a 6.5mm Carcano rifle made by Beretta, but without seeing it or knowing the markings, that cannot be determined. As a military rifle, there is no "owner's manual". However, there is information on loading and firing the 6.5 Carcano available. To use as a repeating rifle, there is a stripper clip that must be used to hold the cartridges.
$125
You don't give us a lot to work on- but Gardone Val Trompia was, and is, the home of Beretta. Among other firearms, they made different versions of the Italian Army rifle, the 6.5mm Carcano. Value of ANY firearm is dependent on the specific model, and condition. The Carcanos are not especially high dollar collector's guns, and may sell for $100-200. Visit the website for surplusrifle.com for some more information, and see if yours looks like the ones there. As a side note, the 6.5mm Carcano was the rifle reportedly used to assassinate Pres, John Kennedy.
Beretta
You need to know the make, grade and model. 270 mag rifle could be anything
Strong enough to be sold and laywer approved.
Made in Italy