Gold coin values
Melt values calculated live from each product's own fine gold content, at the current spot price of $4,417.29 per troy ounce. Melt is the metal value, not a dealer offer.
Purity is not standard across coins
Bullion coins split into two camps. The 22 carat group - Eagle, Krugerrand, Sovereign - alloys the gold with copper and silver so the coin survives handling. The 24 carat group - Buffalo, Maple Leaf, Philharmonic, Britannia since 2013 - is .9999 fine and marks far more easily.
Neither is worth more per ounce of gold. A 22 carat one-ounce coin and a 24 carat one-ounce coin contain the identical troy ounce and are worth the identical amount at melt. The difference is durability, gross weight and personal preference.
Identifying what you actually have
Diameter is the fastest tell. A Philharmonic is 37mm and visibly wider than everything else; a Maple Leaf is 30mm and the smallest of the one-ounce coins; a Sovereign is 22.05mm, almost the same size as a quarter-ounce Eagle but holding slightly less gold.
Where a coin carries a face value it is stamped on it, and that face value is symbolic - a $50 Eagle has never been worth $50. Measure the diameter and weigh it before assuming which coin you are holding.