The ornamental design for a displaydevice for a printing machine, as shown and described.
FIG. 1 is a perspective view of a part of a display device for a printing machine showing our new design;
FIG. 2 is a top plan view thereof;
FIG. 3 is a front elevational view thereof;
FIG. 4 is a right-side elevational view thereof;
FIG. 5 is a left-side elevational view thereof;
FIG. 6 is a rear elevational view thereof; and,
FIG. 7 is a bottom plan view thereof.
The portions of the part of the printing machine shown in broken lines form no part of the claimed design. The broken line showing of the junction piece in FIGS. 2, 6 and 7 is for the purpose of illustrating environment and forms no part of the claimed design.