This is the second U.S. special delivery stamp, providing the addressee with
immediate delivery between the hours of 7 a.m. and midnight.

The service began October 1, 1885, and was limited to free delivery offices and
post offices in towns of 4,000 population or more.

At that time, there were 555 such post offices.

The Act of August 4, 1886, extended the service to all post offices,
necessitating a change in the wording in the design of the stamp to note that
service had been extended.