You can find the value on the USPS web site. You want publication 604a that shows pictures of the non-denominated stamps.
What was the cost of a postage stamp in 2001
The current cost of a US postage stamp is 44 cents
39¢ http://www.usps.com/communications/news/stamps/2006/39/
4cents
There are several different unmarked flag stamps. You need to look at this site http://pe.usps.com/text/qsg300/Q604a.htm and find the picture of the actual stamp you are interested in.
I don't see any writing on the flag. The lower right of the stamp has the year in small numbers, but there is nothing on the flag itself.
The cost of the first postage stamp (Scott #1) in 1847, was 5 cents.
A first class stamp costs 46 cents in the US. Each additional ounce is 20 cents.
A First Class Stamp is 44 cents.
According to the USPS website, under "Buy Stamps", then "Rate Change", the brown background non-denominated US Flag stamp is $.41. The US flag is one of the most popular subjects for a Postage Stamp and can be found on dozens of them. The value of each will be dependent upon condition and rarity. You would have to identify the specific stamp to determine the value.
In the US a first class stamp cost 5 cents in the US. A postcard cost 4 cents. It went to 6 cents in January of 1968.
39 cents