If you look on the bottom of the receiver, where the barrel lugs come through, it may say which Citori model it is. and the shape of the wrist or pistol grip are all important factors in pricing. If a "325" or "425" those are Sporting Clays guns. Some early 325's have one fixed choke and one screw in. That seems odd and a detriment; WRONG! For older Clays guns those are the highest sought after!! Most 325's went to England, some to France and very few to the USA. Current numbering is 725!
Lightning is a highly desirable hunting gun but is usually 8 ounces heavier, A Superlight is very light, straight stock and 24" barrel, They look cool but are hard to hit with and kick a little extra! Then there is the Upland Special (I have 2!) 26", English stock and very sleek! Mine are older fixed choke models and in 20 and 28 gauge (Grade VI). These are just about the ultimate in O/U bird guns. But I wouldn't want one in 12 gauge. The screw in chokes require a certain diameter and these sleek guns have to have the barrels flared to accommodate the tubes, thereby ruining the fine lines and maybe balance. (still not near as good as a small frame Parker or Smith SxS! But at a fraction of the price!)
Any "Blue Book of Modern Gun Values" will help you figure out the exact model, but is worthless establishing fair market value!
My remaining 12 gauge Citori is a 30" 425. A previous owner used it for waterfowl hunting in salt marshes! It has a tendency to rust in the cut engraving. Otherwise, great gun! My 20 gauge 425 is 28" and is considered a little short for Sporting Clays and long for Skeet, balderdash! It is the most balanced and lively Citori I own! (I also have two Superpose from Belgium, there is NO comparison!)
I'm sure this is more than you ever wanted to know, but I hope it helps.
Ivan