You need to know the coin's mint mark and condition. The mint mark, if it exists, is found on the reverse under the eagle. No mark = Philadelphia, O = New Orleans, S = San Francisco, CC = Carson City. Retail values for all mints except CC would range from maybe $15 in average circulated condition up to $20 or so if the coin has almost no wear. An 1880 Carson City dollar, however, would run from $90 to $200. If you do have a CC dollar, you'll need to have it examined by a reputable dealer or other expert since the mint mark is frequently counterfeited. Finally, as you may have noticed by reading some of the many, many other posts on this site, the motto E Pluribus Unum appears on ALL U.S. coins so it doesn't really identify a coin.
A silver dollar with the national motto E PLURIBUS UNUM on it dated 1880 is actually called a MORGAN dollar, most all US coins have this motto somewhere on the coin. It's a very commoncoin with a retail value of $36.00-$42.00
Currently a 1880 S Morgan silver dollar in MS65 uncirculated condition is worth $156.
Please see
If you mean a 1880 Carson City Morgan dollar? circulated examples run from $100.00-$300.00
A 1880-S Morgan Silver Dollar that is in a mint state of MS67 is worth: $ 450.00.
1880-series US $2 bills were issued as United States Notes rather than silver certificates. Please see the question "What is the value of an 1880 US 2 dollar bill?" for more information.
August 29, 2009 The more common 1880-CC dollar in MS65 grade has a value of $1625. The less common Proof-like 1880-CC dollar in MS65 grade has a value of $1900. The scarce Deep Mirror Proof-like {DMPL} 1880-CC dollar in MS65 grade has a value of $11,000.
In MS60 Grade uncirculated, a 1880 S Morgan Silver Dollar is worth about $52. In MS65 Brilliant Uncirculated, it is worth over $330.
Currently as of April 2012 a 1880 Morgan silver dollar in MS63 uncirculated condition is worth around 63 dollars.
There were no $1 silver certificates dated 1880. Please check your coin or bill (which is it?) again and look at the related questions for more information. Also note that nearly all US coins and bills carry that motto so it's not something that helps to ID a particular item.
See the related link below for a picture of the 1880 silver dollar.
Responses to questions on Answers.com are normally specific to one item. Please check for questions "What is the value of an 18xx US silver dollar?", where 18xx is 1880, 1881, etc.