We claim the ornamental design for a magazine for holding flat cards, as shown and described.
FIG. 1 is a perspective view from above of the magazine for holding flat cards showing our new design.
FIG. 2 is a perspective view from below of the magazine for holding flat cards shown in FIG. 1.
FIG. 3 is a top plan view of the magazine for holding flat cards shown in FIG. 1.
FIG. 4 is a side view from the left of the magazine for holding flat cards shown in FIG. 1, which is the same as the view from the right of the magazine for holding flat cards.
FIG. 5 is a bottom plan view of the magazine for holding flat cards shown in FIG. 1; and,
FIG. 6 is an end view of the magazine for holding flat cards shown in FIG. 1.
The broken lines and the areas within them depicted portions of the magazine for holding flat cards that form no part of the claimed design.