I think it is a proof coin that entered circulation.
I have 2 just like it, 1x 1999 Year of the Older Person and 1x 1984 Mob of Roos. I have compared the Mob of Roos to my other proof Roos and the two coins looks the same in the non scratched shiny patches.




Sorry the Photos are not great. They do not capture the true shine of the coin when held in hand.