ΔE 6.7, close: similar, with a visible difference side by side. Obsidian Pigment Toner is more saturated than AMT-12 Dark Grey.
Usually, if you are not matching paint already on the model. Close match (ΔE 7). Obsidian Pigment Toner is more saturated than AMT-12 Dark Grey.
The same difference applies the other way round: AMT-12 Dark Grey is 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 AMT-12 Dark Grey on the colour wheel See Obsidian Pigment Toner on the colour wheel
All matches: AMT-12 Dark Grey equivalents · Obsidian Pigment Toner equivalents