IIRC, "Grand Slam" was the name of a large bomb develoepd for the RAF by Barnes Wallis, who developed the bomb used by the Dambusters.

It was the part of a highly accurate precision bombing system.

Auric Goldfinger could have altered the ChiCom weapon to fizzle producing a very low yield detonation that would not destroy the gold but make it too radioactive to be used as the United States reserve. This would increase the value of Goldfinger's gold but would also plunge the United States into a financial calamity. In effect, precision bombing of the financial world with one bomb.