I am an 8 letter word

I am an 8 letter word.
i am kept secret from everyone.
my 2nd, 3rd and 4th letters spell an animal.
my 4th, 5th, 6th, 7th and 8th letters are a weapon.
my 1st, 2nd and 8th letters are used for writing an exam.
my 3rd and 4th letters are the same.
guess what am i?