On older US stamps before 1875, it's difficult to find stamps with original gum. As hard as it may be to believe today, years ago collectors soaked the gum off of mint stamps because the gum was stuck down or the gum was damaging the stamp (dark spots, etc). To preserve the freshness of the stamp, collectors simply soaked off the gum.
Never hinged copies of stamps before 1875 do exist, but they are very rare. You may find a more common Scott #11, #65, etc with never hinged original gum. But most stamps only have part of their original gum or no gum at all. Scott even prices no gum copies of early US issues.
When buying mint, no gum copies of early US stamps, examine them closely. You may find traces of ink used for cancellation. If so, this is not a mint stamp. It's a used stamp and should be priced accordingly. Sometimes a perforation or two may be removed to destroy any traces of a cancellation. There isn't much you can do about that. There are people who will lighten or try to remove cancellations (also called cleaning a stamp) in order to increase the price of the stamp to a mint, no gum copy.
Be careful when buying mint, no gum early US stamps. Make doubly sure that you're not buying a stamp with an extremely light cancellation or a stamp where the cancellation has been removed. Examine the face of such stamps with at least a 10x magnifier. When in doubt, a certification of expertization would be in order