Matt-Klein, I don't think it's going to be possible to reliably identify or date. There's too much of it missing. Maybe you don't realise just how many purposes there were for our Royal coat of arms (official and otherwise) in various badge-like forms. My opinion stands that it's not earlier than Victorian, based on the style of the arms (and can't possibly be earlier than 1801 because that particular armorial didn't exist prior to that date).
The only other thing I would offer is that the workmanship of the representation looks to be of poor quality execution. The engraving of the mould or stamp from which it was produced is crude. That in itself doesn't mean it wasn't produced for some official use, but it does rather point against it.