ΔE 9.7, close: similar, with a visible difference side by side. Deep Green is a little lighter, more saturated, cooler than Protective Green 1920s-1930s.
Usually, if you are not matching paint already on the model. Close match (ΔE 10). Deep Green is a little lighter, more saturated, cooler than Protective Green 1920s-1930s.
The same difference applies the other way round: Protective Green 1920s-1930s is a little darker, more muted, warmer.
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 Protective Green 1920s-1930s on the colour wheel See Deep Green on the colour wheel
All matches: Protective Green 1920s-1930s equivalents · Deep Green equivalents