FIG. 1 is an upper left perspective view of the new rear firearm sight when viewed from a muzzle end of a firearm;

FIG. 2 is a lower right perspective view thereof when viewed from the muzzle end of the firearm;

FIG. 3 is a front view thereof when viewed from the muzzle end of the firearm;

FIG. 4 is a rear view thereof when viewed from a breech end of the firearm;

FIG. 5 is a left side view thereof when the muzzle end of the firearm is to the viewer's right;

FIG. 6 is a right side view thereof when the muzzle end of the firearm is to the viewer's left;

FIG. 7 is a top view thereof when the muzzle end of the firearm is to the viewer's right; and,

FIG. 8 is a bottom view thereof when the muzzle end of the firearm is to the viewer's right.

The broken line showing of portions of the rear firearm sight in FIG. 7 forms no part of the claimed design.