That humble penny may be more valuable than you think. Bill Walker, a senior numismatist (coin expert) at Heritage Galleries and Auctioneers, in Dallas, offers this list of coin-purse keepers.

Dimes, quarters, and half-dollars dated 1964 or earlier have a 90 percent silver content (dimes and quarters no longer contain any silver) and today are worth about four times their face value to collectors.

The 1995 “double-die” penny, minted in Philadelphia with the word “Liberty” double-stamped on its front, is worth up to $40. The 1972 double-die penny from Philadelphia has all the lettering on its front doubled. It is valued at up to $600.

The 1969 penny minted in San Francisco (look for an S under the date) with the words “In God We Trust” doubled has sold for $7,000 or more. Fewer than 35 have been discovered.

A very small number of Sacagawea dollars were produced with the imprint for a quarter on the heads side. Estimated value: about $50,000 each.