That is a 1999 AHD Diamond Race 72. The test below by Ken Winner rates the board highly. "
Less extreme in that they don't have flaps and aren't generally quite as wide for their lengths, are the boards from AHD, the Fanatic Bee 289 and the two freeride designs from Star Board, the Free 299 and the Go. They all have a length to width ratio of 4.5 or less, something very few boards had as little as one year ago. Particularly notable from this group is the AHD Diamond Race 72. At 28 inches wide and just under nine feet long it's conventional and radical at the same time." The other tester felt the AHD Diamond Race 72 was the most fun to sail of all the boards tested. See below link and more details in photo. I believe one AHD designer at the time was Tom Luedecke of Australia who may have had a hand in this board.
www.americanwindsurfer.com/articles/1999-equipment-test-slalom-light-wind-boards/Probably much better for windsurfing than SUP. Sad to see it being used for paddling not sailing. However at 164 litres, 72 cm wide and being lightweight construction (7kg) should work fine assuming you have a weight of around 90-95 kg maximum although it will work up to 100kg for paddling or more. For SUP you will need a tuttle fin and a paddle. If you want to windsurf (I know you don't) it would be great you will need fin and rig and it may even be good for wind foiling assuming it is deep tuttle. Not a bad board to have. $45 including fin is a good price if that is AUD. Does it include fin ? Does it include sails etc ? Without a fin it will cost you at least $100 for a tuttle fin but for SUP you will need a more traditional dolphin type tuttle fin and not the same as the one pictured which is too deep for SUP in my opinion. If the standard 54 cm fin is included you might be able to sell the fin for more than the board cost you and then buy a smaller cheaper Tuttle for SUP use.