The jtpr entity posted thusly:

Is there a
method to calculate where to place the receiving hole in the top for
the pins or is it trial and (god forbid) error? As I said, I don't
have a lot of time, so I kind of have to do this without a prototype
build first.

Placement of the pins will depend on the geometry of the lid at the
rear of the box. If you round over the top rear, place the pin at the
center of the roundover radius or a little toward the front of the
lid.

I was thinking about the pin idea a few days ago, and thought a nifty
(and puzzling) way to do it would be to drill the holes in the top
deep enough to take the whole pin plus a bit, then drill the sides to
take perhaps half the pin length, and to come very close to the
outside of the box.

Make the hole just a tad larger in diameter than the pin diameter.
Then use a syringe/needle to place a little superglue or epoxy in the
bottom of the side hole. Finally, place the pins (steel) in the holes
in the top, and use a rare earth magnet to draw the pins into the side
holes, so they come into contact with the glue. If the side holes are
deep enough, the magnets will apply plenty enough force for superglue.

A bit of bother, but think of the puzzled looks of those trying to see
your hinges/holes.