Taking the bike computer apart - more difficult then first thought

The bike computer case appears to comprise a top and bottom half case. There are no screws holding these two halves  together so I can only assume the manufacturer used a press fit. I've shoved a screw driver blade in-between the small space between the top and bottom case, jiggled it about, but the case is not budging. Hmmm, I was hoping I could take it apart without damaging the casing. Next step take is to take it to a colleague who can X-ray it for me - I might then get a clue on how to open it