York Safe combination number missing

I just recently purhased a York safe from an auction with no combination. The safe door is open and I was able to retrieve the following information: Underwriters labratory no.: 42223 Safe Manufactures National Association: 1X 11358 Cat. No. 2015-1 Also there is an arrow on the inside of the door behind the combination dial. I can actually see the mechanisim move when turning the dial. Is there something to this where I can watch the tumblers or place something in it to figure out the combination? Thanks!