Possible Clues:

• Coins once found by men on board belonging to crew
• Pirate plunder ... or a hint to interpreting an appropriate number of squares in this puzzle
• *Treasure chest coins
• Five-and-three, say, in old money?
• Historic phrase for Spanish dollars
• Men put energy into old contest for real money
• Half-pick way around ice sheet in fog to get old coins
• Bits of shell used as money