what is the value of a 1914 $2.50 gold coin?

Answer 1

Indian Head $2.50 Quarter Eagle Gold:

Dated 1914:
Average circulated = around $230-$250
Nicely circulated with fewer marks = around $270
Almost uncirculated = $300 to $325
Uncirculated = $500 onwards

Dated 1914-D(with a small 'D' to the left of the word 'Five'):
Average circulated = around $230
Nicely circulated with fewer marks = around $250
Almost uncirculated = $270 to $300
Uncirculated = $350 onwards

If you sell it to a dealer, you'll get less.

Answer 2

US coin? If so, it's worth somewhere between 575$ (3) and 700$ (1)

The quality will make it vary. Some (2), may fetch up to $5751