Benjamin Miller had an abundance of the early stamps called carrier stamps. Used in cities in the mid-1800s, carrier stamps paid for mail delivery or pick-up. At the time, this was a special service; letters were normally carried only between post offices, not street addresses.
The original 1851 Franklin carrier stamps were not used for long. Easily confused with a Franklin postage stamp, they were replaced within two months by stamps with an eagle design. These Eagle carriers were used for several years, making them less rare. Starting in 1875, the Post Office made special printings of both stamps for collectors. Miller collected those later stamps, too.