What is the value of a 1928 US 2.5 dollar gold piece?

My January 2005 edition of The Coin Market lists its retail value at $135 Very Fine to $230 Uncirculated.

UpdatedNumismedia lists the following approximate retail values as of 09/2010:

Very worn condition - $204

Moderately worn - $240

Slightly worn - $258

Almost no wear - $300

Uncirculated - $372 to $3,920 depending on quality

DISCLAIMER: The values quoted are the best available, but may vary due to market fluctuations. Also the wholesale (buying) price of a coin will be less than the selling (retail) price. A reputable coin dealer will be able to give a more accurate valuation based on inspection of the coin.