1st-class

n.1.a class mail comprising letters, postcards, and other mail sealed against inspection, having a higher priority than second, third, or fourth-class mail; - it is the highest class of mail not handled in a special manner, as is registered or priority mail.
References in periodicals archive ?
A hypertext editor in 1st-CLASS HT allows developers to organize information into "cards.
1st-CLASS HT also lets developers use hypertext to build custom screens and windows.
1st-CLASS HT is available for use on IBM PC, XT, AT and compatible personal computers and may be purchased direct from 1st-CLASS Expert Systems, Inc.