You can only deal with a very small portion of a collection at any one time, so the question of it being in a bank vault is not a major problem. You might want to look at a small group, but it is difficult to imagine a study that would require hundreds of coins in hand at the same time. Coins are bought individually and are best viewed as a single object. Two coins side by side invariably leads you to say one is better than the other, whereas in many respects they will still be equal. Not all coins are available in identical grade, toning, or shape, but all were purchased on their individual merits.