Any chance you can move the hinge tabs & hinge to the other side w/o breaking them off. Anneal, straighten and re-bend.
Making the hinge to the other side gives you a left hand PB.
What you'd be looking at in the pic posted is the back of the left hand PB.
No new parts to make.
Your existing door engraving would be visible when the door was opened in a LHand installation. Either burnish it out or add something to it to make it acceptable for the interior. Name, date, etc.
You'll still have to re-engrave the outside of the box as the now plain bottom will become the outside. But you'll have to on a new one as well.
Go gently on the new screw countersinks too. Use a wider angle if possible to avoid a cut through and a large screw hole.
Or just make another one! and sell this one.