The US made 2 varieties of $20 coins.
D = Denver
S = San Francisco
CC = Carson City
O = New Orleans
D = Denver
S = San Francisco
mint mark is to the left of the value on the reverse.
On the reverse just to the left of the arrows
The mint mark for the 1909 Half Eagle is located on the reverse {eagle} side of the coin just to the left of the arrow points.
Assuming the coin is circulated and no mint mark retail values are $312.00-$420.00
From about $1300 to $75,000 depending upon the mint mark and the condition of the coin.
mint mark is to the left of the value on the reverse.
The mint mark on a $5 gold coin from that era is on the reverse (tails) side, just below the eagle.
The P is the mint mark for Philadelphia.
On the reverse just to the left of the arrows
depending on condition, about $300
A date is needed. Post new question.
The mint mark for the 1909 Half Eagle is located on the reverse {eagle} side of the coin just to the left of the arrow points.
Please post a new question with the coin's date and mint mark.
Assuming the coin is circulated and no mint mark retail values are $312.00-$420.00
From about $1300 to $75,000 depending upon the mint mark and the condition of the coin.
With an "S" mint mark on the reverse, about $1,000 for its gold content. With no mint mark, $6,000 or more. But any such coin should be inspected by a professional to ensure that it's not counterfeit or altered.
It depends on the year of issue, post new question.