The concept behind pawning, where lenders use personal property as collateral, dates back to ancient Greek and Roman Empires. But for the first time, Denver-based Pawngo has taken the idea online with enough venture backing to go national. Customers email pictures and descriptions of their goods, and Pawngo gives a rough estimate of value. The owner ships the item to Pawngo overnight, and Pawngo can then inspect it in person and make a firm offer. If the item’s owner doesn’t accept the firm offer, Pawngo ships the item back at its own expense.