The last year an "O" Mintmark was used on any US coin was 1909 and no silver dollars were made after 1935. Look at the coin again and post new question.
About $27.
42cents
About $150.
"DO" isn't a mint mark. The mint mark on a silver dollar for that year is on the reverse (tails) side, just above the letters "do" in the word "dollar."
If the coin has any wear the value is for the silver, about $8.50
2 to 4 $
The value of a 1941 Walking Liberty half dollar coin can vary depending on its condition and mint mark. In circulated condition, it is typically worth its silver content. If in uncirculated condition or with a rare mint mark, it can be worth significantly more to collectors.
About $27.
42cents
About $150.
"DO" isn't a mint mark. The mint mark on a silver dollar for that year is on the reverse (tails) side, just above the letters "do" in the word "dollar."
One Dollar
about $25 depending on condition and mint mark
They are still found in circulation, have no silver and are only face value
If the coin has any wear the value is for the silver, about $8.50
Assuming it's worn from circulation, it would be worth around $3 for its silver content.
Please look at the back of the coin. It's a circulation half dollar, not a bullion piece. Regardless of mint mark, its value as of 07/2008 is in the $7-8 range.