Back in the late 1960s, the Shell Oil Company ran massive advertising campaigns using collector coins. I am not sure if they helped the oil company, but they sure helped coin collecting. Back then (not like now) you could find valuable coins in pocket change and it became popular to scour every penny for the elusive 1909S VDB, worth hundreds of dollars. Other rarities, such as the 1918/17 standing Liberty quarter were also hunted with gusto.
Shell capitalized on this pastime and gave collector coins to folks who bought their gasoline.
Presidential sets, like the one shown here (click) were the most popular. But this 'States of the Union' set enjoyed a good run.
Here are current retail prices for these sets:
STATES OF THE UNION SET (50 MEDALS)
Completely new, in original packaging: $35 US dollars retail price
With one or more coins missing: $3