I find this incredibly interesting and hope you will too. The pattern is New England Glass Company's [ NEG co.]"BLAZE" c. 1866? The patent drawing of the mold is c.1847 by Joseph Magoun of the NEG co.The idea behind the patented mold was to eliminate most of the unsightly mold line in pressed glass stemware.
WORKING THE MOLD:
As "B" in the drawing is the only hinged two piece in the mold this is where the mold line would occur. The "plunger "H" would be lifted from the mold and "G" [top] lifted off, the hinged section "B" opened, then the "plug" "A" incorporating the cup shaped foot is pushed upward thus releasing the article from the mold.The article would be taken out the top of the mold and be subjected to the fire to form the foot thus polishing out most of the mold line there. Although the patent drawing shows a round baluster stem, the patent concept later refined for a multi-sided stem where the mold line would follow along two edges of the stem and be mostly hidden to the eye.
A more complete drawing of the patent can be seen here:
https://patentimages.storage.googleapis.com/fa/87/6a/757236fccd1a69/US5302.pdf Finished pieces in this pattern and type of mold can be seen at;
https://www.eapgs.net/pattern-details.php?idx+781 The line drawings in the link are from a NEG co. catalogue c. 1868-1869.