ΔE 23.4, loose: different enough that you should pick on purpose. Brass is noticeably darker, warmer than Ancient Gold.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 23). Brass is noticeably darker, warmer than Ancient Gold.
The same difference applies the other way round: Ancient Gold is noticeably lighter, 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 Ancient Gold on the colour wheel See Brass on the colour wheel
All matches: Ancient Gold equivalents · Brass equivalents