As you know, the Silver Coin is a drop item. All mobs have a chance of dropping it. You can also get this coin in Lore events or by finding Silver Coin Chests. This item cannot be obtained by donation.
Bodahn has brought these chests from distant and dangerous lands, they may contain:
100k – 180k adena
Scroll +50% of XP/SP for 2 hours
1x Gold Coin
Pirate Eye Patch Accessory
Pirate Hat Accessory