This box was made by Ron Koch (author, decoy historian, and decoy maker), it does have butt joints, however dovetailed construction does exist. The dimensions are 8 inches high, by 10 inches wide, and 16 inches long.
The box is great in a skiff. Just make sure the angles of the gun yokes allow the gun to point over the top of the skiffs bow. It also is great to use on a dove hunt.
These shell boxes, like old wood decoys, marsh skies, trapper paddles, continue to gain in value the more they are used. Hope this helps. Mike