The ornamental design for a pan for a weighingdevice, as shown and described.
FIG. 1 is a top front perspective view of the pan for a weighing device;
FIG. 2 is a top plan view thereof;
FIG. 3 is a bottom plan view thereof;
FIG. 4 is a front elevation view thereof, the rear elevation view being a mirror image thereof;
FIG. 5 is a left-side elevation view thereof, the right-side elevation view being a mirror image thereof; and,
FIG. 6 is a top front perspective view thereof, with the broken lining showing of environmental structure made for the purpose of illustrating the use of the pan for a weighing device and forms no part of the claimed design.