Two factors make it hard to be of much help. First the number of Colt Series 70 in bright nickel that I see traded is limited so we have a " thin market." Second the guns I see trade are at Centeral Texas gunshows and this may have little to do with where you live. That said, Two have been offered at the Premier shows in Fort Woth and San Antonio for $2200 with no takers. One sold a few months back in San Antonio for $1000 after no buyers at $1200. Two with the box have sold for $1500 and $1700. I would give $1200 to $1250 which is not that much more than is ask for 1911A1s that have been nickled.
Wonder why a picture is needed to answer this question? D
We typically need photos to opine on value of a firearm. Besides, we like to look at photos of Colt firearms. Seeing photos motivates us to offer our opinions. If you put out the effort to post photos, we put out the effort to tell you what you are looking at, and answer your questions.
That said, IMHO, you ought to try to negotiate down the price by one or two hundred dollars, then go ahead and buy the Colt at whatever the resultant price turns out to be. I do not see how you could get hurt, buying that gun (assuming REALLY new) for $1300. Be aware that representing a gun that has some wear on it as a new gun is a common misrepresentation.
A fairly recent pistol advertised as new but with no box is a little suspicious. It may have been a shooter that was Flitzed back to look new. Look at the barrel for signs of scuffing. Where the bushing rides on the barrel and the top of the chamber would be a good place to look.