1984 $1 aust. coin R M punched either side of her neck

Hi Tiddyathome,
Welcome to the forum.
It does sound like someone has messed with the coin. I have heard of many coins being found with numbers struck into the coin afterward but not heard of letters before. I'm sure others will comment on this also.

Thanks very much for the welcome. I'll have to let my mother know.

I've got 5 Aussie coins with different stampings as follows:

1997 $1 (Smithy) with 0 stamped on both sides
1975 50¢ with an E stamped on the obverse
1967 20¢ yesterday with a 0 stamped on the obverse
1968 20¢ with you stamped on the obverse
1998 $2 with upside down 3 stamped into HM's neck

With the first 4, all are stamped to the right of HM's neck. I'm not sure if the 0's are letters or zeros.

On the Australian Coins, Tokens and Banknotes Forum there's been a bit of speculation lately about who's responsible, but nothing concrete has been established.