Bimetallic heaters function the same way as embedded bimetallic protectors. These were controlled by a thermostat employing a bimetallic spring. The balance consisted of a circular steel balance wheel with two bimetallic strips attached diametrically. A problem with bimetallic standards was that the metals' absolute and relative market prices changed. This type of balance wheel had two semicircular arms made of a bimetallic construction. Since 2000, many bimetallic 10-ruble circulating commemorative coins have been issued. Bimetallic commemorative 10-ruble coins will continue to be issued. In 1998 a bimetallic commemorative 10 rupee coin was released. Older devices used bimetallic junctions and were bulky. Bimetallic 5 dinar coins were introduced in 2002. Bimetallic coins are sometimes used for higher values and for commemorative purposes. In 1977, aluminium-bronze 200-lira coins were introduced, followed in 1982 by the bimetallic 500 lire. A bimetallic 100 fils coin was introduced in October 1992. In 1994, a bimetallic 10-dollar coin was introduced. In 2003, bimetallic 200 and 500 franc coins were introduced, replacing smaller denomination notes.