Platinum Bullion coins are produced at the Philadelphia Mint and West Point Mint.
W is the monogram of the designer, A. A. Weinman. Mint marks were on the backs of most coins up till 1968 and in any case the West Point Mint didn't exist in 1941. Please see the Related Question for more information.
It's the designers initial. If it was a mintmark it would stand for West Point. The West Point mint didn't make any such coins.
'w'stands Washington the capital of The United States Of America on the US coins. The W stamped on US coins stand for the mint at West Point where it was made. Today, the West Point mint makes all of the commemorative and precious metal US coins.
The mint at West Point began by striking cents from 1973 to 1986. These cents had no mint mark and can not be distinguished from those struck at Philidelphia. In 1988 West Point was officially made a mint and today the mint mark "W" appears on coins struck there.
Philadelphia, Pennsylvania. Philadelphia is the only US mint to not put a letter mintmark on the coins made there. [ The mint at West Point has , at times, struck coins for the Philadelphia mint with no mintmark]
On a US coin it's the mint mark of the West Point Mint. Normally West Point only manufactures special collectors' coins such as commemoratives and bullion pieces, but in 1996 it struck Roosevelt dimes for the coin's 50th anniversary. Be careful to distinguish the W mint mark from the same letter on Mercury dimes and Walking Liberty halves. On these coins it's the monogram of their designer, A. A. Weinman. In any case they were struck decades before the West Point Mint was opened.
Actually an unknown number of Bullion 2011 Silver Eagles have been struck at the San Francisco Mint since late this summer. This was done to supplement the output of the West Point Mint. They have no mintmarks and are indistinguishable from the bullion coins from the West Point Mint. Some of the coins have been certified to come from the San Francisco Mint and sold on E-Bay, H.S.N. and other dealers.
If the coins has a West Point mint mark it's on the reverse to the left of the eagles tail. Starting in 2001 all Silver Eagles are struck at West Point. Only proof and burnished coins bear the W mint mark.
The West Point facility didn't begin striking coins until 1973, and didn't become a full-fledged mint until 1988. On top of that, it has never made circulating coins bearing the W mint mark - only collector and bullion coins.
Circulating coins:Philadelphia (P mint mark since 1980, no mint mark before that)Denver (D mint mark)Proof coins:San Francisco (S mint mark)Bullion coins:Philadelphia and West Point (W)
Coins are produced by the US Mint which is part of the Treasury Department. The Mint currently strikes coins in 4 facilities: Philadelphia, "P" mint mark since 1979/80 on all coins made there except cents Denver, "D" mint mark on all coins made there San Francisco, "S" West Point, "W" Since the 1970s only Denver and Philadelphia have produced coins for circulation, while proof coins are made in San Francisco and special collectors' coins, bullion coins, and commemoratives are made at West Point.