Mike, this could easily be placed in the "which came first, the chicken or the egg" category. However, based on your provenance and the unofficial yet official rule we S&W collectors follow and that being a gun's shipping date = the birth date then K260001 is the first Combat Magnum, regardless when it came off the production line the same day as 260003. Your's had a definate destination where as 003 did not, at least not in Nov, 1955 when both guns were being produced. It is also pretty clear the intent of S&W higher ups to insure that Bill Jordan received the first example of the model he was primarily responsible for. Just my thoughts on an interesting friendly debate.
Chuck