Historic Glass Factory Artifact WHAT IS IT?

Artifact excavated from an historic glass factory site in Pittsburgh. It's a partial ring made of a fire/ heat resistant brick material. Looks like it would've had two 1/2 rings which fit together. See yardstick measurements. Big & heavy! WHAT IS IT? Wondering if it would've held a pot of molten glass? Wonder what the purpose of TWO pieces was ... like a hinge mold or hinged holder? Need a glass historian!