Lovely old EAPG glass jelly dish, oak leaf pattern, late 1800s or very early 1900s vintage.
This is a cover, not a mold which would leave a pattern on the jelly. The leaf pattern is on the exterior of the dish, the inside shape is smooth. It's about 8" long end to end.
This has very little discoloration from age, though there's fleabites and some roughness to the rim from use. No serious chips or cracks.