I am stamp collector who has gotten back to collecting after 40 years, I received a huge amount of stamps from a recently deceased collector. I'm sure she removed many stamps from stamped envelopes that she received asking for donations. I remember those with strips of transportation coils put on them. She also owned a large department store in Iowa and saved some of the many stamps she had purchased for her business. So, my question is how do I tell if the coil strips are mint or removed from such envelopes. Did they all have dull gum? I see no shiny gum on any of them. I never collected during that time, so I don't have any to compare.
It depends on the issue. Some Transportation Coils have an almost invisible gum - looks like there is no gum. Others have dull gum or shiny gum. If in doubt let us know which stamp you have trouble with
Get out a magnifier. Many of the transportation coils have a texture to the dry gum - the most obvious on is fine diagonal lines, others show horizontal lines (often the lines are broken) or a harder to describe wavy texture, Fins some ones you are sure are used, or soak off the gum on a cheap one (you may need to rub the gum side as this type of gum tends to be tenacious) and compare the used stamp to ones you are sure are mint. You will be able to see a difference. Some like the 32c ferryboat only exist with shiny or semi shiny gum.