It wouldn't surprise me if they were (as has been noted elsewhere) either getting some of the metalwork from Premier or, when Premier changed their fittings, actually bought the tooling and kept using these a la Camco and DW (though obviously Premier didn't go bust).
And carrying on in that speculative mode, it also wouldn't come as a shock if in the later days, just as Camco did, you could order specific fittings for your kit (Rogers fittings, particularly, show up as "factory" on Camco quite often).
None of this based on fact of course - just imagining what a shop with such a small production run might have allowed.
I've still yet to speak to anyone who actually bought and picked up a kit from the factory though there must be a bunch of these people floating around Brisbane.