Foxfire,

A true left handed double is a "mirror image" of the norm.

The lever will work to the left, not the right.

The front trigger will fire the left barrel instead of the right.

The stock will cast to the left instead of the righr, and any cheekpiece will be on the right.

Triggers on doubles are canted to favor the hand that is to use them. Sometimes this is quite pronounced. The typical right-handed double has the triggers turned so that their faces angle to the right. That gives better contact across the faces of the triggers for the right index finger. A lefty will notice that his finger contacts the left edge of the triggers instead of comfortably engaging the trigger faces. On a true left handed gun this is set up opposite - for the left index finger.

A south-paw who orders a bespoke gun will get all this from the gunmaker.

I am told that triggers on a RH double can be switched and re-shaped for the LH shooter. The triggers are not particularly hardened, and often can be artfully re-shaped under heat.

Again, that is just what I have read or have been told. Fortunately, I am right-handed.

As an aside, several years ago I bought a best quality 12 gauge shotgun. When it arrived, I found the stock had been bent for a LH shooter. It was a RH gun, plain as day, and the triggers are markedly canted for the RH shooter. I had the stock bent to my dimensions, and that solved the problem.

Best,
CptCurl