The ornamental design for a mortarboard with electronic tubedisplay, as shown and described.
FIG. 1 is a perspective view of my new design for a mortarboard with electronic tube display;
FIG. 2 is a top plan view thereof;
FIG. 3 is a first side elevation view thereof; and,
FIG. 4 is a second side elevation view thereof.
My mortarboard design is characterized by six cylindrical top-view electronic tubes positioned on a circular arc adorning a rounded plate atop a mortarboard.
The broken lines shown represent the portions of the mortarboard with electronic tube display that form no part of the claimed design.