Get it in writing, documented by a CIA historian, a picture of it in the Shah's hand, anything else you can possible connect to the Shah, and then have all the evidence itemized and notarized. Otherwise, there will always be naysayers.I know the CIA agent who was presented the gun. I can't say more than that.
And even if you get all that, there will still be some detractors. But you'll have a leg up on the story.