Pyrex Percolator on stove?
Pyrex percolators made after 1940 were not intended to be used directly on a heating element as stoves made after 1940 had a higher burner heat level that those made in previous years. (Presumably, those made before 1940 were placed directly on a burner.)

The Pyrex percolators I remember had a wire 'grid' or 'heat spreader' that was to be placed on the burner and then the percolator sat directly on that. If memory serves me correctly, they came in a variety of shapes. See below for an example.