MFC marbles are all machine made - in other words, they will never have a pontil. NEVER! I know because I have spent 1000's or hours researching MFC as well as conducting numerous archaeological excavations at the factory site - including inside of the building - RIP
Leighton only made melted pontil hand gathered marbles at his numerous marble factories. I know because I conducted archaeological research at every factory site which is still available for study.
The Germans on the other hand made ground pontil hand gathered marbles. This is published in a great book by Herbert Kuhnert as well as in other period (circa 1850) documents where the Greiner family displayed their wares at International Expositions, etc.