Mark,
Value really increases (and decreases) due to the variance of % remaining of original blue finish and % remaining of original straw finish on the small parts.
You can browse these two pages from the Simpson LTD site for their current 1915 offerings...you will notice quite a price spread due to just a difference of 1-2% ratings.
Those % ratings are very subjective as well. I find a seller has them in his mind higher and of course, a buyer has them lower in his mind...
You will also see that having a proper holster, TD tool, and matching magazines adds tremendously to value as well.
This is what is called a "rig". Some rigs are true vet bring-backs, others are put-together rigs by collectors and sold as such, and even some are put-togethers claimed to be original bring-backs with phonied-up bring-back doc's as well...
http://www.simpsonltd.com/index.php?cPath=179_181
http://www.simpsonltd.com/index.php?...sort=2a&page=2