At first glance of those enlargements, I'd immediately call them wood dowels or some meaty, chopped off shovel handles but behind the plexi, there's definitely something "more" than that. I agree about the perforations of a .50 cal. barrel but that's a helluva long barrel. Would put the body of the .50 pretty much right up against the rear of the pilot's instrument panel! Lastly Wurger, I'm not sure I agree with you regarding the serial #. I read it as 42-12375 or 42-12575. Anyhoo, that's my usual .02 cents worth.