Okay Bertie, it is a permutation lock.
Except, the letters are in a set postion and the numbers are in a set postition.
So why would you want to divide by 8! I don't get it.
(Okay, I just got it,you are just being padentic about the lay persons word combination )
In your example
Afterall, if I told you that the three numbers on a simple lock were 2, 3 and 7 you wouldn't necessarily expect them to be in that order. You would have 3! = 6 different orders to try. Yes that is true
It is a 3 digit tumbler - order obviously matters - the number of possiblilities is 10*10*10=1000
The right combination (lay speak) is obviously a permution - order matters so the probablilty of getting the right combination is 1/1000
The probablity of getting 2,3 and 7 in any oder is 6/1000
Don't worry - I am really just talking to myself here - I do that. 
If order does not matter than the probability would be greater. I'd multiply by 8! (not divide) but this would not be right I do not think. It would be ok if every number/letter were different but what if all the numbers were 7 and all the letters were A then it would not work! Plus, in Alan's implied scenario the letters occupy 4 specific spots and he numbers occupy a different 4 specific spots.
Ummm 

