The most common sulphide that I have seen is the white porcelain figure in crystal glass. There are some variations of sulphides out there, and they can be pretty rare.
Hard-to-find sulphides that have colored glass (like green or blue), and the figures in the marble can sometimes be painted.
There are two things to keep in mind when it comes down to the condition of the marble. The glass itself is always something to look at for chips, cracks, and even clarity. But don’t forget to examine the figure itself.
Old sulphides will have air bubbles in the glass, and the figure will be off-centered and sometimes there will be a pontil mark. They were meant to be played with, and they often were. Sometimes they were played with to the point where they are chipped and even cracked.