Plastisol is the standard lining material used in metal closures for vacuum packing glass bottles and jars. Plastisol is a flowed-in compound, usually a dispersion of pvc resins in plasticizers. It forms a solid, self-bonding, sealing gasket in the closures. Plastisol liners are used in metal twist-off and metal continuous thread screw caps for use on hot-pack food products where the preservation of a vacuum is essential.
Condition: This circa 1960s vacuum glass bottle is in good condition, I tested it for heat retention by filling with boiling water 190-200*F and after one hour the temperature remained over 175*, so it is very capable of serving actual thermos uses. The outer case has some signs of wear, see HD pictures for complete details.