One answer isn’t going to fit all of your questions. In the early days the size and color of the Treasury Seal on notes varied greatly, as did the colors. In general they changed colors to thwart counterfeiters and to differentiate between series of notes.
To determine what kind of a note you have, look at the wording above the central portrait. The most common note in circulation today is the “Federal Reserve Note.” You will find that the seal color is green. Following is a listing of other 20th Century US notes that you may find in circulation or at numismatic sales or events:
Silver Certificates— Blue Seal
US Notes— Red Seal
National Bank Notes— Brown Seal
Gold Certificate— Yellow Seal
The numismatic value of paper money is based on rarity and condition. While early issues of “large-size” notes may hold numismatic value in various conditions, the enormous quantity of issues during the 20th Century dictate that few “small-size” notes will attain a significant numismatic value in less than uncirculated condition. If your note is in crisp, uncirculated condition you may want to seek the advice of a local numismatic expert.
The chances of your Continental Currency note or coin being genuine are quite slim. Thousands of copies of the dollar-sized coin have been made, usually in soft pot metal. The first check for the notes is to see whether the signatures are in a different ink than the rest of the note. If it is different, then your note may be genuine - but it still could be a counterfeit, so don’t quit your job until it has been examined by a qualified expert. Show it to your local coin dealer first and then he or she can advise you whether it’s an obvious fake or a piece that should be submitted for authentication.
Silver Certificates are one of several forms of notes issued by the U.S. Government. Like the Gold Certificates, each note was backed by bullion stored in the Treasury vaults. Before 1935 it was legally possible to exchange a Silver Certificate for a dollar’s worth of silver and after that, for one dollar’s worth of silver bullion. However, the legal tie between silver and our circulating currency ended in 1968 by an Act of Congress, although Congress did allow one full year (June 24, 1967 - June 24, 1968) for redemption of silver certificates. To distinguish the different types of notes, look above the central portrait. On today’s notes you will see “Federal Reserve Note.” These notes are backed only by the Government’s promise to pay.
Silver Certificates do have a collector value over face, based on the amount of wear. Someone, such as a local coin dealer, would have to examine the note. As a general rule most of the 1935 series and later issues of $1 Silver Certificates have little value unless they are crisp uncirculated grade - meaning no wear and no folds of any kind. The values for higher denominations go up sharply as the face value of the note increases.