The ornamental design for a crane for a revolver, as shown and described.
FIG. 1 is a front, top, left side perspective view of a crane for a revolver showing our new design;
FIG. 2 is a rear, bottom, right side perspective view thereof;
FIG. 3 is a front, elevation view thereof;
FIG. 4 is a rear elevation view thereof;
FIG. 5 is a left side, elevation view thereof;
FIG. 6 is a right side, elevation view thereof;
FIG. 7 is a top, plan view thereof; and,
FIG. 8 is bottom, plan view thereof.
The broken lines in the figures are used to illustrate environment and unclaimed parts, in which the claimed design is embodied, and form no part of the claimed design.