What is a glass seal?
It's a plate of glass attached to the casket at the rubber gasket around the top. It is locked down before closing and provides an extra barrier to moisture.
Glass sealers are offered in high-end caskets, mostly hardwoods, and coppers and bronzes.
Are you in the business??
No. But things don't change much in the funeral business. I remember all this from 30 years ago.