Standing Liberty quarters don't have a W mint mark. The West Point Mint didn't start making coins until 1988. They have either no mint mark, a D, or an S. The "M" is the designer's initial.
If you can't see the date (a common problem with early SLQ's), it is really worth its silver value, about $3.25 as of 06/2010.
If you can see the date and mintmark, you need to check a price guide to know what it would be worth. Low-grade SLQs can go for as little as their silver value or well into 3 digits depending on the date and mintmark.
The 1927 Philadelphia issue Standing Liberty quarter is common, the "M" is the designer's initial. In average circulated condition the values are $8.00-$15.00.
A 1919 standing Liberty Quarter Dollar in good condition (G4) is worth: $40; if its mint state is MS60, the value rises to: $175.00. If there is an S or D mint mark at the bottom of the left-hand pillar (i.e. at Miss Liberty's right side) the value range is roughly $85 to $1200.
There are Walking Liberty half dollars and silver bullion coins, but the Walking Liberty design was never used on a quarter.If you're referring to a Standing Liberty quarter, its value depends very much on its condition, mint mark, and date. Please enter the question "What is the value of a US quarter?" for a specific answer. "19xx" of course is the date on your coin, like 1918 or 1930.
the "M" on the front of a Standing Liberty quarter is the monogram of the coin's designer rather than a mint mark. Please see the Related Question for more information.
$20-$1,300
A 1919 standing Liberty Quarter Dollar in good condition (G4) is worth: $40; if its mint state is MS60, the value rises to: $175.00. If there is an S or D mint mark at the bottom of the left-hand pillar (i.e. at Miss Liberty's right side) the value range is roughly $85 to $1200.
1919 makes it a Standing Liberty quarter, so the mint mark is on the obverse (heads) side, just to the left of Liberty's feet. D is Denver, S is San Francisco, and no mark is Philadelphia.
If there is no mint-mark letter to the left of the date, $5 if worn, up to about $28 in like-new condition. If there is an "S", the range is $5 to $35.
It depends on its mint mark and exact condition. See http://www.numismedia.com/fmv/prices/stdqtr/pricesgd.shtml for an example of the price range.
The "M" isn't a mint mark. It's the initial of the designer H. MacNeil and it's on all Standing Liberty Quarters and most coins of this date have heavy wear and valued at $3.50-$7.00
"Mercury" dimes were minted from 1916 to 1945.Standing Liberty quarters were minted from 1916 to 1930.Please check again and post a new question with the coin's date and mint mark.
With no mint mark or an "S" near the date, this coin is worth about $6 in average condition. If it has a "D" it's worth about twice as much. FWIW, the coin is called a Standing Liberty quarter. Most days, heads don't walk, LOL!