The ornamental design for an external dual-disk mini-backplane, as shown and described.
FIG. 1 is a front, top and right side perspective view of an external dual-disk mini-backplane showing my new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a rear elevational view thereof;
FIG. 4 is a top plan view thereof;
FIG. 5 is a bottom plan view thereof;
FIG. 6 is a right side elevational view thereof;
FIG. 7 is a left side elevational view thereof;
FIG. 8 is a front, top and right side perspective view of the external dual-disk mini-backplane with its front cover open; and,
FIG. 9 is a front elevational view of the external dual-disk mini-backplane with its front cover open.
The broken-line disclosure is understood to represent portions of the article in which the claimed design is embodied, but which forms no part of the claimed design.