bedroom door code

Hi. I've been really liking the game, but I've gotten stuck trying to get the code to Mason's secret room. Been so busy trying to find the 9th BB card, that I've drawn a blank after trying about 10 things. Can someone point me in the right direction? Thank you.
Keep on grabbing objects and look at stuff in your inventory. It took me a long time to find that code and when I finally did, oh boy did I feel dumb! :oops:
Thank you. Got wound up looking for the cards andmpore Mike and Ike's, but did devote time trying stuff on the door. I guess I'm dumber than most because NOTHING gave me a nudge except 'CARDS.' :lol: