Sounds like a good find. I buy a gun once in a while on Gunbroker, usually get them at a good price, lots of times when not so many are bidding on them. I call them squeakers! Lots of time I watch a number of guns that are interesting, many times the gun bid/information is hidden between gun company catalogs, parts, etc, etc. I will have been looking through a number of pages and all of a sudden a gun for sale will pop up that's been on auction for a while that I didn't see and has few bids and will go for a good price. Case in point is a Springfield M1 Garand I bought recently, March of 1954 barrel and approx. serial number range, all part drawing numbers match serial number and barrel-excellent shape, throat erosion and muzzle wear both in #1 range scale--a real find and beauty. It was a squeaker, only had three other bids and sold way below what others of its shape had been selling for. It had been on auction 3-4 days before I saw it. It pays to watch the auction bids if you are into on-line auctions. I've never been unhappy with any buys, always communicate with seller before bidding.
Have fun shootin your Signature Model Colt. I picked up a new, unfired, in box (even had its brown paper outer cardboard box as yours had) Signature 3rd Model Dragoon back in early 2008, several months after I bought a Cimarron 2nd Model Dragoon. Payed the same for the Sig model as I did the Uberti. Don't care what some may say, the Signature Models are still Colts, say so on the box, on the gun, and on all the papers. Don't care a tinker bell if they won't 'paper' with Colt. I called Colt once and the Colt represenitive said that they ARE Colts, just won't 'paper'. Who cares! Love them Colt cap and balls!