Very good job on the research. Not at all sure however that the "AR" can be taken literally as the coin definitely being of silver composition as it was and continues to be used in referring to copper nickel iterations of former actual struck-in-silver coins of that denomination(s).
As a side note there are some transitional issues of coins of a date that should be actual silver being struck in pattern form in Cu-ni (ie 1923 3d, 1923, 1924 shillings and the very rare 1946 shillings)....
So these 1960 crown coins may well exist in silver but definitive proof would be required: wight, specific gravity and XRF testing, etc.