It could be D/A - I had one given too me that is. Whichever it is though, the row nearest to you, the highest pitched, will be G or A and the one furthest away will be C or D. The other common configuration, which I doubt this is, is a G/D, used extensively for Morris Dance.

Easiest way to find out - Use a tuner! Middle button, left hand side, on the push in note will be the 'home' note of the key for both rows. Not got a tuner? Download one on you phone if you have a smart phone. No smart phone? Borrow a tuner! :-)

Cheers

DtG