Bullion coins are coins made from precious metals. Their market values are determined by their inherent precious metal contents. As such bullion coins are mainly kept as investments or stores of value.

Most of the bullion coins available are made from silver or gold. A few also come in platinum though, including the American Platinum Eagle, the Canadian Platinum Maple Leaf, the Australian Platinum Koala, and the Manx Noble. Here's a quick rundown of each of these four platinum bullion coins:

The American Platinum Eagle:

The American Platinum Eagle bullion coins were first minted and released in 1997 by the United States Mint. They are offered in four varieties:

1. 1/10 ounce (oz.) coin - With a face value of USD10, 3.112 grams (g) in weight, 0.95 millimeters (mm) thick, and 16.5 mm in diameter.

2. 1/4 oz. coin - With a face value of USD25, 7.78 g in weight, 1.32 mm thick, and 22 mm in diameter.

3. 1/2 oz. coin - With a face value of USD50, 15.56 g in weight, 1.75 mm thick, and 27 mm in diameter.

4. 1 oz. coin - With a face value of USD100, 31.12 g in weight, 2.39 mm thick, and 32.7 mm in diameter.

All coin varieties consist of 0.9995 fine platinum. One interesting feature of the American Platinum Eagle coin is that its reverse design changes every year.

The Canadian Platinum Maple Leaf:

The Canadian Platinum Maple Leaf bullion coins were issued from 1988 until 2002 by the Royal Canadian Mint (RCM). They were offered in four varieties: 1/10 oz. coin (with a face value (FV) of CD5), 1/4 oz. coin (FV: CD10), 1/2 oz. coin (FV: CD20), and 1 oz. coin (FV: CD50).

Two additional varieties, 1/20 oz. coin (FV: CD1) and 1/15 oz. coin (FV: CD2), were issued by RCM, but only in 1994. In 2009, the 1 oz. coin was reintroduced. All coins, which have legal tender status in Canada, consist of 0.9995 pure platinum.

The Australian Platinum Koala:

The Australian Platinum Koala bullion coins were first released in 1988 by the Perth Mint, the oldest currently operating mint in Australia. The coin comes in 1 oz. variety, with a face value of AD100. As with most other bullion coins, this value is much lower than the coin's bullion value.

On the coin's obverse is a koala, in sunken relief (i.e., lowered from the coin's plane); on the reverse is Queen Elizabeth II. The coin has legal tender status in Australia.

The Manx Noble:

The Manx Noble platinum bullion coins were minted from 1983 to 1989 by the Pobjoy Mint, the leading private mint in Europe. The coins were offered in five varieties:

1. 1/20 oz. coin - With 1.555 g platinum content, 1.556 g in weight, and 13.9 mm in diameter.

2. 1/10 ounce coin - With 3.11 g platinum content, 3.112 g in weight, and 16.5 mm in diameter.

3. 1/4 ounce coin - With 7.776 g platinum content, 7.78 g in weight, and 22 mm in diameter.

4. 1/2 ounce coin - With 15.552 g platinum content, 15.6 g in weight, and 27 mm in diameter.

5. 1 ounce coin - With 31.103 g platinum content, 31.119 g in weight, and 32.7 mm in diameter.

The coins have no currency value. Their value, rather, is equal to their respective platinum contents. All coins consist of 0.9995 pure platinum.

On the coin's obverse is Queen Elizabeth II, along with these texts: "ISLE OF MAN" and "ELIZABETH II". On the reverse are a Viking ship, the denomination, platinum content, and the words "Platinum fine".