ΔE 9.3, close: similar, with a visible difference side by side. Hammered Copper is a little lighter, more saturated than Tarnished Steel.
Usually, if you are not matching paint already on the model. Close match (ΔE 9). Hammered Copper is a little lighter, more saturated than Tarnished Steel.
The same difference applies the other way round: Tarnished Steel is a little 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 Tarnished Steel on the colour wheel See Hammered Copper on the colour wheel
All matches: Tarnished Steel equivalents · Hammered Copper equivalents