I claim the ornamental design for an interlocking concrete masonry block, as shown and described.
FIG. 1 is a perspective view of an interlocking concrete masonry block showing my new design;
FIG. 2 is an end view thereof;
FIG. 3 is a front view thereof; and,
FIG. 4 is a top view thereof.
The broken lines in the drawing views are included for the purpose of illustrating a portion of the interlocking concrete masonry block that forms no part of the claimed design.