Well, the probability of items is the same on almost all levels, and

is Coeff 3. Coeff 3 items appear roughly 1/8 of the time. There are 23 coeff 3 items that can appear for you (I think [I excluded

,

, and the BoS stuff]), so your chances of getting

on any one level are about (1/8 ) * (1/23), 0.0054, 0.5%, or
1/184.
One time I had a Moneybag appear on Lv. 1. The Moneybag is a coeff 5 item, and yadda yadda yadda, the chance of that happening is (1/700) * (1/8 ), 0.00018, 0.02%, or
1/560.
