A "special stamp" refers to a unique or unique-looking stamp that is different from regular stamps. It could have a special design, commemorate a specific event or person, or be used for a particular purpose. Full definition
Everything this time of year is about Christmas — there are special greeting cards, special stamps, special lights, special decorations, special festivals, special music. (religion.blogs.cnn.com)
(Unfortunately, her «Stamp Out Invasive Species Act,» which would direct proceeds from a special stamp to federal agencies for programming, seems to have stalled in Congress.) (suncommunitynews.com)
Know for shure that it will be a nice gift and then made with a special stamp figure for the recever... I give it a try very soon. (sparklelivingblog.com)