A coin collection's value is tied directly to condition, and even light scratching from coins rubbing together can measurably reduce a coin's grade. Keeping every coin in its own protective flip or album slot is non-negotiable.
Pro tip: Graded and slabbed coins in hard plastic cases travel the safest; if any of your high-value coins are still raw, consider having them graded before a long move.
Watch out: Loose coins rubbing against each other during transport can cause fine scratches that lower a coin's grade and resale value.