You can tell by removing the case. You need essentially no mechanical (and absolutely no electrical) knowledge or ability. There are several small screws to remove (they're quite obvious). Then take the cover off. Now, with the faceplate facing you, in the right rear corner are some green chips that are labeled "WIMA" chips. You can read it with the naked eye, although it's quite small.
Your other option is to ask Theta to run a serial # search. They'll charge you $25 for it though. Good luck.
Your other option is to ask Theta to run a serial # search. They'll charge you $25 for it though. Good luck.