Just found out Tigerleprechaun42 used "G-WLBY" for a fan made redesign of Wallaby 2. Both the Australian regs I came up with (VH) are taken in real life, but they're not helicopters nor emergency aircraft.

@TheIsraeliSudrian I appreciate it. I know that (VH) is the Registration Prefix for any Aircraft in Australia. (G) Is the Registration Prefix in the UK. For the United States, (N) is the Registration Prefix. Example... G-WLBY for Wallaby 2. N754AN for an American Airlines Boeing 777-223ER. And VH-OJT for a Qantas Boeing 747-438. By the way... Tigerleprechaun42 on DeviantArt? That's me.

@BA38P Now I get why this account posted some of "their" (your) other work here. Thanks for explaining.

I know the other prefixes since I checked the Wikipedia list to find the one for Australia (and recalled G for UK from other sources). Here, it's 4X.