As you can see, this little stopper glows brilliantly under a black light. It is yellow Vaseline glass and probably was once a stopper for a perfume bottle.
The pattern is hobnail. It measures 1 1/4 inches across the top. From the top of the neck to the top of the stopper, it is almost one inch. The neck is 1/2 inch long by 1/16 inch wide.
If you have a black light display, this item would greatly enhance your collection.