Bull’s-eye pane
Glass Dictionary

A glass pane with a pontil mark surrounded by concentric ridges. This was the central part of a large pane of crown glass.
Alternate Spellings:
Bull’s-eye panes
Bullseye pane
Bull’s eye pane
Artwork Examples:
A glass pane with a pontil mark surrounded by concentric ridges. This was the central part of a large pane of crown glass.