The ornamental design for a bagfastener, as shown and described.
1. Bag fastener
1.1 : Perspective
1.2 : Front
1.3 : Back
1.4 : Left
1.5 : Right
1.6 : Top
1.7 : Bottom
The material of a bag fastener is metals; the subject design is used by attaching to bags and handbags; the figures are photographs substituted for drawing representing the following: FIG. 1.1 shows a perspective view of the design, FIG. 1.2 shows a front view thereof, FIG. 1.3 shows a rear view thereof, FIG. 1.4 shows a left side view thereof, FIG. 1.5 shows a right side view thereof, FIG. 1.6 shows a top view thereof and FIG. 1.7 shows a bottom view thereof.