Prior to 1965 and passage of the Coinage Act of 1965 the composition of the US dime, quarter, half-dollar and dollar coins was 90% silver and 10% copper. With the passage of the Act, the current version of the quarter is a cladded coin with two layers of cupronickel (75% copper and 25% nickel), on a core of pure copper. It currently costs 11.14 cents to produce each coin (as of 2011).
The hunter-gatherers of Eestexas disagreed over which Old Time coins were more valuable. Most, like the hunter Jorj Rainbowstar preferred pure silver coins since they were inherently more valuable. Others, such as the shaman Madyu, preferred those that were silvery on the sides but sandwiched copper. These, shaman agreed, were more magical. For one, no smith could duplicate such a sandwiching. For another, they had larger numbers than those that were silver. Shamans could not agree as to what it meant but all agreed it had magical significance.
Thes coins were commonalty carried as necklaces for convenience and a way of displaying ones wealth.
After The Change, Topanga was small enough to run mostly on barter but coins were needed for trade with other communities. Gold and Silver were good but even metal-sandwich coins retained some value since no one could make them any more. When Jared Tillman went up to Chatsworth on a diplomatic trip, he paid for his and his son's meal at Sierra's with a dozen sandwich quarters.
While trade went on with gold and silver, day to day commerce was done with coins including Old Time ones. Some preferred silver coins while others like the sandwiched silver and copper instead. When Jeff Mendoza bought a dozen old popular science and science fiction magazines from Luke, he paid him with solid silver since that was Luke's preference. In fact, Mendoza paid extra as way of a tip by using "cartwheels" or silver dollars which weighed slightly more than four quarters or two half-dollars.