1981 Scalloped 20 Cents

Seems odd to be posting to this thread all these years later but I have this coin in my possession and can't see it in any other recent threads. It's about to be sent off for grading. My mother in law was a bank teller for most of her working life. Back in the early to mid 80s she stumbled across an odd looking 20c piece at work, swapped it for a normal 20 and took it home. It sat forgotten about in a jewelry box until last Thursday when it was discovered in a clean up. She sent me a photo and asked if I knew what it was. Got to say, the resulting research left me pretty stunned. She'd been sitting on one of Australia's rarest decimal currency errors for over 40 years with no idea.