The ornamental design for a samplecassette for a diagnostic instrument, as shown and described.
FIG. 1 is a right rear perspective view of a sample cassette for a diagnostic instrument showing our new design, where the top portion is optically opaque and the bottom portion is optically transparent;
FIG. 2 is a front right perspective view thereof;
FIG. 3 is a top plan view thereof;
FIG. 4 is a left side elevation view thereof;
FIG. 5 is a right side elevation view thereof;
FIG. 6 is a rear view thereof;
FIG. 7 is a front view thereof;
FIG. 8 is a left rear perspective view thereof; and,
FIG. 9 is a left front perspective view thereof.
The bottom view is plain and unornamented and is not part of the claimed design.