I have never heard of MISB before but then I am not in the collecting World. My view was always that if it Stated Brand New in Box (BNIB) that it was unopened and New In Box (NIB) was new but may have been opened. Trevor mentions shrink wrap, as far as I know Plarail never used it so if you do have one sealed like that it might send up a caution flag. Thats one of the draw backs from the Japan Auctions is not having that Buyer to Seller direct communication.
I used to be in the Vintage PC Game collecting and there, listings would state new in manufacturers sealed box, or manufacturers shrinkwrapped box. But then came the easily available shrinkwrap machines at businesses or at home and the fakers started to show up. My friend bought a particularly rare, valuable game listed new in manufacturers shrinkwrapped box and when he cut open the shrinkwrap and looked inside the CD case was wrapped in paper towel.
I used to be in the Vintage PC Game collecting and there, listings would state new in manufacturers sealed box, or manufacturers shrinkwrapped box. But then came the easily available shrinkwrap machines at businesses or at home and the fakers started to show up. My friend bought a particularly rare, valuable game listed new in manufacturers shrinkwrapped box and when he cut open the shrinkwrap and looked inside the CD case was wrapped in paper towel.