I'm far from an expert but I believe the double trigger is for real. I think it could be a Mauser Model 66. And I think it may be cocked as well. Don't know enough about Mauser's to tell if the safety is engaged.
It appears some organizations, rather than obtain permission (pay for) for images, invert them, as a way of justifying free use. Same with this "mailer". I think they're fooling themselves by inverting the image. It's still theft of intellectual property, if they didn't obtain permission. And if they did.....why invert the picture? I don't think this would fall under "fair use", as it is neither incidental, nor is it a satire, nor is it an article about the "picture".
Alf