The ornamental design for an attachmentdevice, as shown and described.
FIG. 1 is a top perspective view of an attachment device of my design.
FIG. 2 is a top view of the attachment device of FIG. 1.
FIG. 3 is a bottom view of the attachment device of FIG. 1.
FIG. 4 is a back view of the attachment device of FIG. 1.
FIG. 5 is a front view of the attachment device of FIG. 1.
FIG. 6 is a first side view of the attachment device of FIG. 1; and,
FIG. 7 is a second side view of the attachment device of FIG. 1.
The broken lines shown in the figures are included for the purpose of illustrating portions of the attachment device and form no part of the claimed design. Randomly dashed lines represent surface shading.