I'd suggest getting the pistol 'Lettered' by the Colt Factory. Once you have the date of manufacture/sale, and possibly who it was sent to:- (Dealer/Private purchase etc)then you can check the local records of Tombstone (Newspapers, local library, etc) and determine when it was, that the said 'Lester' who is said to have owned this handgun actually died.
If the pistol was made after Lesters death, you just bought an old pistol, but it it was shipped to him, or was sold in Tombstone before Lester died, there may be some truth in the story.
Either way you've got yourself a nice looking Colt. Telling the story a few times may even get you an offer of mucho bucks from a wannabee collector.
Harry