Purity
Look for a stamp on the old gold item indicating its purity. Most gold is mixed with other metals to make it sturdy enough to handle. Pure gold is 24 karat. Most old gold items are 10, 14, 18 or 22 karat gold. The higher the number, the purer the gold.
Rarity
Seek rare gold items. Many of them have value for their scarcity as well as their gold content. This is especially true of gold coins. Certain denominations, years and mint marks on gold coins can increase their value by thousands, or even millions, of dollars.
Quality
Consider the quality of the old gold. The quality of old gold significantly impacts its value. Gold jewelry, flatware and coins that are dinged and worn are worth less than pristine items. Damaged old gold is worth little more than its gold content.