Here is a wonderful example of the 15-cent value from the short-lived 1869 Regular Issue described in the article below.

One of the greatest joys of collecting United States stamps is the fact that there is almost always an enjoyable and
intriguing story behind them. There are, for instance, great tales behind the discovery of some of our major errors as with the
24-cent inverted airmail stamp of 1918, which was purchased by a stamp collector in Washington, D.C.

In 1869, after the U.S. Post Office Department had been issuing stamps depicting our Founding Fathers for 22 years (since
our first stamps in 1847), a decision was made to change the format of America's postage stamps from rectangular to
square—and depict not only Washington, Franklin and Lincoln, but pictorial designs such as the signing of the Declaration of
Independence.

Thus the definitive issue of 1869 was born. With four of the stamps printed in two colors, it is considered today to be one of
our most beautiful sets. But people didn't think so in 1869! In fact, there was a giant public outcry when the 1869's were
issued. People didn't like the smaller format and they especially didn't like the pictorial depictions on the stamps. Newspapers
all over the country published editorials in protest of their issuance. The POD was aghast at what they had done and
immediately went back to the drawing boards to produce a brand new issue.

Consequently, the 1869's were only in formal use for less than a year. They were replaced in 1870 by what many deemed as a
rather boring set of formal bust-like depictions of famous Americans. Best of all, though, the lovely 1869's are still within the
budgetary reach of most collectors. They are tiny colorful jewels on an album page and, contrary to when they were issued,
they are very, very popular with philatelists!