1 Although any individual may develop a case of pinworms, the infection occurs most frequently in school children between 5 to 10 years of age.  Pinworm infections occur in all socioeconomic groups; however, human-to-human spread is favored by close, crowded living conditions. Spread among family members is common.
Before they start collecting, stamp collectors try to identify the types of stamps. These will help them segregate and sort stamps according to their classification. On its basic concept, there are three main classifications of stamps â special, commemorative, and definitive.
In addition to the regular and commemorative issues of the USPS you will find back-of-the-book categories such as airmail and special delivery, revenues and duck stamps, possessions including Hawaii, booklet panes and plate blocks and plate number coils, postal cards and postal stationery and USPS Year Sets.