CREATE TABLE table_39074 ("Denomination" TEXT, "Metal" TEXT, "Weight" TEXT, "Shape" TEXT, "Size" TEXT)

Which metal has a size that is 26mm (across scallops)?
SELECT "Metal" FROM table_39074 WHERE "Size" = '26mm (across scallops)'
SELECT "Metal" FROM "table_39074" WHERE "Size" = '26mm (across scallops)'