The ornamental design for a ladder mounted device and system, as shown and described.
FIG. 1 is an isometric view of upper and lower portions of a ladder mounted device and system;
FIG. 2 is a left side view thereof;
FIG. 3 is a right side view of thereof;
FIG. 4 is a back side view thereof;
FIG. 5 is a front side view thereof;
FIG. 6 is a top view thereof;
FIG. 7 is a bottom view thereof; and,
FIG. 8 is an isometric environmental view in which upper and lower portions of the ladder mounted device and system are shown coupled to a stepladder.
The broken lines shown in the figures are for the purpose of illustrating portions of the ladder mounted device and system and form no part of the claimed design. The broken lines showing a stepladder in FIG. 8 are for the purpose of illustrating environment and form no part of the claimed design.