Blown glass stopper dating from early to mid 1900's. The upper portion is hollow and pointed at the top.
The entire stopper 3 1/8" long. The lower section is ground to fit a bottle and is 18mm (5/8") long and 16mm (3/4") at the base. There are several chips on the lower part, as seen in the photos.
Many old bottles, cruets and decanters have lost their stoppers, perhaps this will fit one of yours.