Scott #1897 or perhaps #2225(coil)
The stamp can be purchased new or used for 15 cents, which pretty much means that a dealer isn't going to pay you anything for one.
Identify the exact stamp using a catalog. This may involve learning about perforations, watermarks and colors as well as condition. The catalog will provide a value. The value is what a collector could expect to pay for a stamp in fine/very fine condition. If selling, most cases you would be lucky to get 75% of the catalog, unless it is very valuable, then an auction would be worth looking into.
The most common American catalog for identification is Scott's. Others are Stanley Gibbons, Minkus and even the US Postal Service Catalog of stamps.
1c 1 cent
Yes, it is still valid for 1 cents worth of postage. Note that the year indicates the date of the Omnibus, not of the stamp. Scott # 1897 was issued in 1981.
This is Scott #1897. This stamp is not from 1880s, that is when the omnibus that is pictured is from. It was issued 100 years later in the 1980's and has a minimal value and can be purchased for 15 cents. A dealer isn't going to want to purchase just one.
it's a bicentennial bill with the stamp of the day and cancelled the day it was printed.
Two-dollar bills are generally worth two dollars. Adding a postage stamp to it wouldn't affect the value if the bill. The stamp itself, if rare, might be worth more than two dollars.
As of today 45/100 of a dollar or 45 cents
There have been many pictures on the $1 postage stamp. The most recent stamp pictures Scott Number 3766 shows 'Wisdom.'
What was the cost of a postage stamp in 2001
postage stamp
the postage stamp had cost $00.32 in the year 1993
The current cost of a US postage stamp is 44 cents
how much did a postage stamp cost in 2016