What do you mean a proof? You thinking like a printing plate? If the text is backwards, it would be quite okay to assume it's a printing plate for labeling or whatever for Plymouth Binder Twine. Would be cool to find out how the plate made it to TX though, especially since their mfg and distribution was outta the north east. But hey, a cool little relic likely from the around the WWII era, a few years before even. Can you get a better, unblurry image?