Can somebody tell me what key this song is in? ( In terms of guitar, or any instrument tuned to C)?

http://www.youtube.com/watch?v=ZX14TMvBGFw

I absolutely love it, and it's so jazzy and bluesy, but I just can't
find the key to play in terms of my guitar. And please don't give
give me the constant banter about training my ear, I'm trying, just
please, if you could help me. Thanks!!