ΔE 48.8, loose: different enough that you should pick on purpose. Ancient Copper is a little darker, much more saturated, warmer than Radiant Platinum.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 49). Ancient Copper is a little darker, much more saturated, warmer than Radiant Platinum.
The same difference applies the other way round: Radiant Platinum is a little lighter, much more muted, cooler.
ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.
See Radiant Platinum on the colour wheel See Ancient Copper on the colour wheel
All matches: Radiant Platinum equivalents · Ancient Copper equivalents