I can't say who manufactured that particular regulator, but there's nothing magical about adding a second primary body to a single body reg. All you need is to remove the high pressure gauge from the original primary body and check the threads whether they're righty or lefty.
When you order a second primary the thread for the passthrough port (where you'll install your high pressure gauge) has to match the gauge, and you'll need to get a nipple that has the correct threads for both ends. Both should be easily obtainable, folks expand primary regulators with mismatched bodies all the time...
Cheers!