Bagman - Charlie is correct, although we have stopped (just recently) making left hand Mariners.
When Spyderco made "left hand" models (which we have done since '81), they were all true left hand models in that they were mirror images. The models that we make now are right hand models, left hand capable, but the serrations are not mirrored.
If you can find any of the left hand models of thepast, grab them. They are nice. They are also rare.
As we experiment with new locks, we are keeping left handers in mind. Then the only adjustment to make a left hand model would be the reverse serration.
sal