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I looked tonight and thats the same one i found, but you could try calling the duty free and see if they know the number (and if not anyone of the brokerage's should know), their number is 344 - 3000, if i go through the border in the next day or two i'll ask for the number.
Now that i think about it, if you can't get the info you need through the port, try calling the head office in great falls, as that where we had to go through for my brother to finish going to school down south. (oh yeah the port director's name is Larry Overcast BTW).