Where is the mint mark on a twenty dollar gold coin?

The mint mark on $20 gold coins minted from 1849 to early 1907 is located on the reverse [tails] side of the coin just beneath the eagle. The mint mark for the Saint-Gaudens $20 gold coin minted from late 1907 to 1933 is located on the obverse [heads] side of the coin just above the date.