It's a remarkable coincidence that he's found himself with a large amount of an unknown variant of Leia blasters and Jawa blasters and Luke sabres and God knows what else. He's been terribly unlucky.
Seriously though, similar to what's been said above, as someone who briefly owned two of these they are identifyable by feel compared to originals which are just a bit softer. While, at first, i just thought they were a strain of original i hadn't encountered, I'm quite confident I'd recognize similar again now that I know better.
For now....