Special Features:

Important-agency name and code number must appear as part of the indicia in the upper right corner below postage paid statement; this may not be handwritten, typewritten, or rubber stamped; only a machine printing process is acceptable by the u.S. Postal service; there are no restrictions as to method of application of the return address; only the requirement that a complete government agency return address be placed above the words official business and penalty statement

Properties:

An envelope, usually made of a paper product. The face may be plain or preprinted with or without an open or glassine address window. The closure may be a gummed flap or a button and string fastener. When required a smaller envelope may be glued on the right face of the larger envelope. The interior may have a printed opaquing design and/or contain chipboard insert(s). It is designed for mailing correspondence/letters; records, or exposed and developed radiographic film. Excludes envelope, photographic negative; envelope, radiographic film mount, dental; and envelope, transparent.