Since it is based on debt and not a tangible commodity it could be the u.s. dollar. Texas just authorized it's first Gold backed state bank. Lakota Bank did it several years ago. Texas is also the only state with a completely independent utility grid.

When Texas agreed to join the union of American states It joined by contract as a independent republic not as a territory. The independent West Florida Republic was never asked but was added to The Florida Territory by Presidential edict. (executive order). The Republic of West Florida ,boardered roughly by the Black and the Apalachicola rivers.