In the 1870s and again in the 1980s, the Post Office issued stamps and stamped envelopes that were used by agencies of the Federal Government to send mail. These are referred to as "official stamps" or "penalty stamps" because of the penalty for private use.
The official stamped cover in Figure 1 is number UO77 in the US Scott Catalog. The Scott Catalog says that this particular type of stamped envelope was used to send US Savings Bonds and occasionally by the US Air Force Academy and US Air Force recruiting stations.
This particular cover is neither. It was sent by the Federal Home Loan Bank Board (FHLBB) on November 10, 1988. At the time, the FHLBB was a government agency that chartered, regulated, and insured the deposits of savings and loan (S&L) associations. The FHLBB was superseded by the Federal Housing Finance Board in 1989 following the thrift crisis of the late 1980s.
I was the recipient of this cover, but unfortunately, I did not save the enclosure. In 1988, I worked in the research department for the U.S. League of Savings Institutions, a trade association for S&Ls headquartered in Chicago.