The people selling it have most likely made sure to store the SN and package it in a way so that it wouldn't oxidize. I'm sure it's fine but from the picture I'm unable to determine whether or not it would be a good container so you should trust the sellers over us.
Just make sure the container is airtight and sealed shut perfectly, if possible, ask the people selling the SN to you in order to make sure.
There's nothing to worry about.