2004P US solid copper five cent piece

The United States five-cent piece, also called a nickel, is composed of 75% copper and 25 % nickel.
There were four varieties of the nickel five cent minted, Shield Type, Liberty Type, Buffalo Type, and Jefferson Type.

The Jefferson Nickels weighed 5 grams, were made of .75 copper and .25 nickel (except in the years of 1942 - 1945 when the composition changed to .56 copper, .35 silver, and .09 manganese), and they had a diameter of 21.2 millimeters. The Jefferson Nickel Five Cent were minted in Philadelphia, Denver, and San Francisco.
http://www.thecoinalley.com/nickelfivecent.html

2004-2006 Saw Big Changes in a US Nickel Coin That Had Remained Virtually Unchanged for Almost 70 Years.

The Westward Journey Nickel Series

These new nickels were produced in 2004 and 2005. They feature Thomas Jefferson on the obverse as in previous years. The reverse designs commemorate the bicentennials of the Louisiana Purchase and the Lewis and Clark expedition.

The new 2004 Nickels have two new designs on the reverse.
The Peace Medal reverse was modeled after the Indian Peace Medals that Lewis and Clark took with them on their expedition to give to Native American chiefs and other important leaders as a token of goodwill of the United States.
They had a portrait of President Jefferson on one side and symbols of peace and friendship on the other.

The Keelboat reverse depicts the boat that Lewis and Clark used during their expedition.

The 2005 US Nickel coins feature a new, more modern version of Thomas Jefferson along with two new designs on the reverse.
They also feature the word Liberty in Thomas Jefferson's own handwriting.
The first was a return of the American Bison after nearly 70 years.

The second features a view of the Pacific Ocean and the quote from William Clark, "Ocean in view! O! The Joy!"

Interesting Note: William Clark's actual diary entry said, "Ocian in view! O! The Joy!", but the US Mint modified it to read "Ocean", a more standard spelling of the word. They were afraid that collectors would mistake the original spelling as a mint error and hoard the new nickel coins.
http://www.coin-collecting-guide-for-beginners.com/jefferson-nickels.html

TRUE PATINA OF COPPER

Patina is the final result, extending over years and often centuries, of highly varied external influences on copper and copper alloys such as bronze and brass. In addition to the external chemical influences, patina formation depends upon the alloy involved and thickness of the metal surface. Patina therefore varies in color and has different forms, surfaces and thickness.

Dug coins can be preserved in the soil extensively due to the absence of soluble salts, or because an equilibrium has been attained between the corrosion and the neighboring soil.

Vesicular, nodular, lumpy and wartlike forms of patina are considered unsightly, otherwise, natural patina is attractive, and since it is an indication of age, it is generally allowed to remain on coins and other objects.

Patina is formed essentially from the following influences:
• Green patina, leafy green to bluish green, can occur in the form of basic copper sulfate, CuSO4Cu(OH)2, from the sulfur dioxide content of urban air. In the vicinity of the coast it can also contain copper chloride (CuCl) from salt dissolved in fog droplets or copper iodide (CuI, CuI2). It further results from air containing carbon dioxide, in combination with dirt and moisture, or from carbon dioxide in the soil in connection with organic acids and salts, and is then in the form of basic copper carbonate (CuCO3). Finally, green patina is a natural result of verdigris.

• Red patina, bright red through dark red to violet, consists of Cuprous Oxide (Cu2O) produced by decomposition (reduction) of the cupric oxide formed initially. For example, this is caused by organic constituents of the soil.
• Brown patina is either a very thin film or light brown to red and black copper oxide formed through the action of oxygen, or it may be a thick mixture of green and red patina.

Dirt of the most varied form often is a constituent of patina, as are inclusions of sand, rust and similar materials.
FALSE PATINA

All coatings on copper and copper alloys such as bronze and brass possessing a patina-like appearance, but which in contrast to true patina, are white or saltlike or resemble clay or grease can be called false patina.

EDIT: http://metaldetectingworld.com/cleaning_coin_p3_patina.shtml

It's what's known as an error coin. It's a nickel without it's nickel coating.Do not clean or polish it in any way. Find a large coin show in your area and ask a few people what it might be worth to them. It could be minted that way in error (worth about $5-8)OR someone removed the coating (worth nothing.) An error collector can tell.

Good luck.
Joe(everyday it rains it rains...)Nation