I had a Bic Tribal with US-E and I still have in Venice a Drops Slash 98 with US-A, the most common us-box.
In my experience US-E(UROPEAN) is WIDER than US-A(MERICAN). Original Bic fin (Select X-Wave) was perfect in the Tribal finbox, impossible to insert in the box of Slash; on the opposite all ather us box fins were perfect for the Slash, loose in the Tribal.
Don't ask me why but in my actual AHD Seal 88 the box seems to be an US-A with the hole in the middle of box (US-E of Tribal had the hole in the front end of box), but every fin seems to be loose until you screw down it, and at the end it is tightly screwed...
The mystery of us-boxes... powerboxes for everybody!!!