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.
Today, stamps issued by the post office are self-adhesive, and no longer require that the stamps be licked to dissolve the glue on their back. In many cases, post office clerks now use Postal Value Indicators (PVI), which are computer labels, instead of stamps.irmail in the United States Post Office emerged in three stages beginning with the 'pioneer period' where there were many unofficial flights carrying the mail prior to 1918, the year the US Post Office assumed delivery of all Air Mail.