What Is The Value Of An 1873 2.5D Gold Coin?

It depends upon it condition, what mintmark it has (if it has one), and what style the 3 in the date is (there were two different styles for the 3 made that year). If it has the open-3 style and it is in mint condition than it is worth $375. If it has the closed-3 style and it is in mint condition than it is worth $700. Finally if it has an S mintmark than it is worth about $2800 in mint condition. Since I can't see it I do not know its exact value. To have an exact appraisal you need to bring it to a coin dealer.