Sorry Ross, but that signature you have shown says "Ricardo Glass", the mark of artist Richard Lamprecht - not Sean O'Donoghue (note the spelling).
You can see the same signature on the vase in the photos below, which is readily recognisable as the work of Richard Lamprecht. An almost identical item is on ebay at present, offered by a seller who is very knowledgeable about Australian glass, item #231934344141. Further examples of the Ricardo Glass signature may be seen on various paperweights on another collector's website
here.
Sean O'Donoghue's signature has been quite variable over the time, so I agree there is some uncertainty. That's why I asked for a better photo of the signature on the OP's piece for confirmation. (He has even changed his name, but that's another story!)
Trevor