ΔE 17.8, loose: different enough that you should pick on purpose. Hammered Copper is noticeably lighter, more saturated than Plate Armour.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Hammered Copper is noticeably lighter, more saturated than Plate Armour.
The same difference applies the other way round: Plate Armour is noticeably darker, more muted.
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 Plate Armour on the colour wheel See Hammered Copper on the colour wheel
All matches: Plate Armour equivalents · Hammered Copper equivalents