As far as we know, there were only single copies of certain key props, like the live-fire Solo blaster. The Greedo killer only came later, in reshoots, remember. And there were resin castings for the Merr-Sonns and whatnot. But, apparently, only one Solo blaster used in the holster and for live fire.
It's not that much of a stretch to say that there may have only been one hero Graflex. MAYBE two. It's SOP to have backups of key props on films, but sometimes that's not the case. I don't think Roger Christian can be considered reliable when it comes to the details and numbers of the props.