The LTC card seems to be a timecode card:

http://www.adrielec.com/pctclit.htm

Also: the resistors on that one board are IMPRESSIVE.

Looks quite interesting indeed. If I had to hazard a guess, I reckon the smaller cards handles the switchboard and music / advertisement media source, both of which the DJ would've had access to. They would've had specialized software to drive it properly, but probably nothing too out of the ordinary.

It most probably came from a local ABC station, since there isn't that many government funded radio stations around the place.

Interesting! I wonder what they used the timecode card for. Nice find.

Yes it came from a local ABC radio station in Brisbane, apparently a few years ago they cleared out all their old stuff. (I just figured nobody outside Australia would know what the ABC was!) Makes me wonder what kind of equipment it was hooked up to, with that many I/Os on it.

Yeh think any Australian that reads this straight away guessed ABC, easy explanation for others, ABC the Aussie version of the BBC.
Something the same no matter what country your from, Governments holding onto equipment well past their commercial counterparts.
Any pics of the PC itself?

PC itself isn't that great and isn't in the best of condition. Here's a shot of the front panel and some of the rust on the lid. The yellow label says "computer switch" and it looks like it's meant to be behind a panel that folds down, but it's missing. The panel on the right just holds a dust filter for the fans that sit there. Only unusual thing is above the keyboard port there are another two DIN plugs for two more keyboards to be connected, but those are obscured behind the metal panel. I guess this was an option so you could fit three SBC boards in a single case, with a suitable backplane.

Rackmount At case nice!
I keep throwing around the idea of racking my old PC's (I have enough of them) but I know I never will really.
ATX era would be fairly easy, AT's would be almost impossible to do without compromises.

The fact it is rack mount pretty much confirms it probably sat mounted with the phone system/DJ system or whatever it was hooked up to and probably did nothing else but that job.