The tidal range is the vertical difference between the high tide and the succeeding low tide. Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon and the Sun and the rotation of the Earth.
Coin toning can intrinsically increase or decrease the value of coins. Natural coin toning can be quite beautiful. It can also be outrageously ugly. And because beauty is often times in the eye of the beholder, placing a value on a coin due to its toning can present problems.
Remember, not all coins in poor shape are worthless. If older coins have gold or silver in them, they are worth, at minimum, the going rate for either precious metal based on recent commodity prices. With some time and effort, you can determine what your collection is worth at retail value.