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.
This may scratch the surface of the coin and will remove metal from the coin's surface. Any wear or scratches will decrease the value of your coin! Note that silver coins can oxidize rapidly, especially in the presence of sulfur, such as is found in paper products.