Help identify my strop

[Spydie]

Hi I received a strop from my grandpa, and I'm unsure exactly what I have and how to use it. Any help would be appreciated.... It's 2 pieces. The top strop is Theo A. KOCHS Company shell horse hide with the number 200 on it. Then there's a 2nd layer/strop that I don't believe is leather. It has labels of keene-edge silk finish, Hess hair milk lab, and the number 401. I'm sure they are going to need to be conditioned before I use it on my knives, because it hasn't been used in many years but seems to be in great condition yet.