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Without other reference material I can't tell if there are various subtle differences that make mine less valuable or as much.
Bingo! That is quite correct. But getting the knowledge to support all that is not done all at once. An important starting point is matching/having the right references for a particular task.
The Scott Specialized Classic catalog is a good choice for you since you are dealing with a worldwide collection. However, for identifying the special varieties of US stamps specifically it is not the best resource. For that you will need the Scott US Specialized catalog. Any edition within the last 3 years is current enough to help you with most identification matters, so you don't have to pay top dollar for the latest, which just came out about a month ago. The specialized study of other countries will also require specialized catalogs for them and their territorial possessions.
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The stamp with Cuba 2 peso is supposed to be valuable because they were issued in this manner for only a short while.
Slight correction: "2 c de PESO" does not mean "2 Pesos." It literally means "2 hundredths of a Peso" (that is, 2 centavos).
I'm not sure where you got your information about what makes stamps valuable, but longevity of an issue is less a factor than the quantity produced and made available to the public. Collector awareness and demand at the time is another important factor, since collectors were, and are, the main preservers of all that material.
Stamp collectors are bugs on details. For some folks that is the attraction. For others it is the main turnoff.