The 10c "Tuatera" of 2007 is apparently issued in copper-steel as well.
does that mean that is it supposed to circulate or is even circulating?
I don't quite get the "as well" - there was only one version made, to my knowledge, in the new copper-steel "sandwich" used for regular circulating pieces since 2006. As others have noted, it was only made for "collectors", though a small number will have found their way into circulation thanks to the efforts of those who were prepared to scrape all the gooey resin stuff off. Add the cost of that labour to the $9.90 issue price and you make quite a loss :-)
(A little background story to this is that the authorities didn't offer dealers a "wholesale price" for these, so they had to pay full retail, just like the public, so as a result it didn't get much support from the usual resellers.)