In celebration of their 300th anniversary, Gibraltar issued a series of commemorative coins with dates 1704 - 2004 and with various patterns on the back. A complete set of these coins in fully uncirculated condition sells retail for about $25 US dollars. Individual coins sell for a few dollars each (when uncirculated), with the larger denominations ranging from $3 to $10 each and smaller denominations $1 to $5 each.
The prices above are retail prices, i.e., how much a collector might pay when buying coins from a dealer or on eBay. If you have these coins and want to sell them to a dealer, figure that he or she would offer about one-half retail or less.
Circulated coins are worth face value. Only uncirculated coins qualify for the prices above.