Rogue River
The DGG represents either Armi San Paolo or Euroarms S.r.l. which Armi bacame in 1970.
The PN stamping is part of the Proof test marking in Italy.
Elsewhere somewhere around the proof marking (there are two stamped adjacent to one another) will be either some roman numberls or some letters, usually found in a rectangular box.
These letters represent the year the gun was proofed.
Follow this link to find out what these date marks are and the year they represent. (This only works for Italian guns).
http://www.muzzleloadingforum.com/fusionbb/showtopic.php?tid/236956/
The 1860 Colt Army is the successor to the Colt Dragoon pistols which were also .44 caliber.
They were made starting in 1860 and continued to be made thru 1873.
The cylinder engraving represents a Naval battle between the Texans and Mexico. It was Colts way of telling people that they had a real Colt.
Although they are called .44 caliber they shoot a .453 diameter lead roundball (without a patch).
The ball is loaded into the chamber following the powder. The loading lever provides the force to shear off a small ring of lead from the ball as it enters the chamber. This provides a seal against the flames from the firing chamber and serves to hold the ball in place during recoil.
Most modern shooters apply some grease like Crisco over the ball to provide lubrication and to serve as a additional barrier to the flames from the firing chamber.
As mentioned you would need a .45.454 diameter lead ball to load your gun.
3Fg powder is recommended but 2Fg will work in a pinch. The synthetic black powders work well in cap & ball revolvers.
The nipples usually like a #11 cap although some work better with a #10.
Look thru the Pistol Forum for gobs of information about shooting these pistols.
Because your gun is a steel frame (as were the originals) its value could range from $25-$250 depending on the guns condition and where you live.