Antarctic (McMurdo)
McMurdo Station, located at 77 degrees 51 minutes S, 166 degrees 40 minutes E, is the largest Antarctic station. McMurdo is built on the bare volcanic rock of Hut Point Peninsula on Ross Island, the solid ground farthest south that is accessible by ship.

The station was established in December 1955. It is the logistics hub of the U.S. Antarctic Program, with a harbor, landing strips on sea ice and shelf ice, and a helicopter pad. Its 85 or so buildings range in size from a small radio shack to large, three-story structures. Repair facilities, dormitories, administrative buildings, a firehouse, power plant, water distillation plant, wharf, stores, clubs, warehouses, and the first class Crary Lab are linked by above-ground water, sewer, telephone, and power lines.

Recorded temperature extremes have been as low as minus 50 degrees Centigrade and as high as plus 8 degrees Centigrade.

Local features include Mount Erebus (an active volcano), McMurdo Sound (the station's namesake, named for Lt. Archibald McMurdo of James Clark Ross's 1841 expedition), the Ross Ice Shelf, and the ice-free (dry) valleys of southern Victoria Land.

Research is performed at and near McMurdo in marine and terrestrial biology, biomedicine, geology and geophysics, glaciology and glacial geology, meteorology, Aeronomy and Astrophysics, and upper atmosphere physics.
Fred R. Zinkann has made coins in Tantalum material which is a hard blue-coloured metal with a very high melting point, too expensive and difficult to work for coinage. Pewter originally is an alloy of tin with about 15% lead, and sometimes antimony and copper. Modern pewters are usually lead-free. The quantity/patterns of this coin were produced in the following below mentioned metals.
 
Metal Condition Pieces Year Weight Edge
           
Tin (Pewter) Proof 25 1987 5.0g Plain
Silver (.999Ag) Proof Piedfort 05 1987 8.5g Plain, incuse edge lettering
Silver (.999Ag) Proof 50 1987 16.0g Plain, incuse edge lettering
Tantalum (.995Ta) Proof 18 1987 10.0g Plain
Nickel-Silver (NiAg) restrike N/A 1987 (N/A) N/A Plain
Titanium (.999Ti) restrike 20 1987 (N/A) N/A Plain
Fred Richard Zinkann has produced / designed $10 1987 Commemorative coin of McMurdo. The diameter of the coin is 25.5 mm. The restrike coins have a diamaeter of 25mm.

Obverse: Antarctic landscape. McMurdo written on the base of the mountains. "1957-IGY-1987" indicates 30th Anniversary of International Geophysical Year. 

Reverse: Ice Crown "WHERE ALL DOMINIONS AND DIRECTIONS MEET THROUGH WIND AND ICE UMBRAGE" is written. "ANTARCTICA $10" is written in the lower center part of the coin. 
 
I purchased my Antarctica $10 1987 Tin (Pewter) plain edge coin directly from Fred R. Zinkann through his Ebay auction. He sells the coins via eBay, using the nom-de-plume “equillink”.
 
Probably in the end 2005, Fred minted some more of these coins in various metals using the same dies. I managed to grab one piece in .999Niobium, 3.5 grams with plain edge. It is 25 mm in diameter with 1.0 mm thick. Mintage of these coin in Niobium is believed to be 19.
 
Information on Niobium:

Symbol: Nb, Atomic Number: 41, Atomic Weight: 92.90638, Density: 8.57 g/cc, Melting Point: 2477 degrees C.

Niobium is a shiny silver-white metal which is ductile and stable in air at room temperature. The metal will slowly develop a bluish tinge when exposed to air for a long time, and will readily oxidize at temperatures above 200°C. Niobium is chemically similar to Tantalum and as a result these metals are difficult to separate from their ores. It has very good corrosion resistance to diluted acids and certain other corrosive chemicals however it is readily attacked by strong alkalis and hot concentrated acids.
Niobium is used extensively in alloys for corrosion resistance, and in alloys for nuclear reactors. It is also used in body piercing jewelry due to its bluish color. The metal was given it's current name in 1950, prior to that it was called Columbium, a name that industry sometimes still uses to identify the metal.
 
 
Micro-Nations
 
Chiefa Coins