Minsup. Hosetail. Coupling.
https://www.bakers.net.au/part/01348889/coupling-slock-ss-hosetail-sh20-20mm
http://www.westatehose.com.au/products-page/coupling-fittings/maxi-claw-couplings/
I consider myself fairly good at internet research - but after spending a bunch of frustrating hours searching down various paths online and finding nothing close, I posted the base query to an engineering forum. Figured getting it in front of as many eyes as possible was the only way this was going to get done. Took em a week or so and they made a lot of good guesses, and tonight somebody finally dropped this.
Luckily we don't have to feel too dumb, as it is an obscure part- from an Australian fittings company that supplies mines. No indication yet how difficult obtaining one will be, or the correct size - of course they would come in a bunch of sizes.