Lot 156 United States SC#1945/2109, 1981-1984 Commemorative Issues, 6 VFNH Se-Tenant Blocks & 17 Singles. 2017 Scott Cat. $18.70 USD, Click on Listing to See ALL Pictures

6 VFNH Se-tenant blocks of 4 & 8 and 17 singles from the 1981-1894 Commemorative issues.
2017 Scott Cat. for very fine mint is $18.70.
Starting in 1964 to 1967 some selected US issues are tagged with zinc orthosilicate , or calcium silicate in the case of airmail stamps. Both taggants can only be seen with short-wave UV light, which is dangerous to the eyes if viewed directly. Zinc orthosilicate glows yellow green, while calcium silicate glows red orange. All issues from the 1967 National Grange issue onward are normally tagged, and untagged stamps are generally errors, with the exception of the 1968 Airlift issue, and a few others. Gum was generally a shiny dextrine gum until the 1980's when an invisible DAVAC style gum was used for certain printings of the 1954-68 Liberty Issue coils and some values of the Americana issue, as well as definitives from the 1980's and onward. Finally, all stamps to 1956 were printed using the wet method, but during the life of the Liberty issue, dry printing was introduced, and many values exist both wet and dry. Generally dry printings have much sharper and lighter printing, as well as stiffer and glossier paper.