I claim the ornamental design for a base plate for toilet tank with opaque and translucent layer, as shown and described.
FIG. 1 is a top elevation view thereof with the front positioned at the bottom of the figure; the side opposite being a mirror image thereof except showing the translucent layer showing my new design;
FIG. 2 is a top left perspective view thereof, the top right perspective view being a mirror image thereof;
FIG. 3 is a top front perspective view thereof; and,
FIG. 4 is a top rear perspective view thereof.
The toilet's tank which is positioned above the claimed design and the toilet's bowl which is positioned below the claimed design form no part of the claimed design. The top layer of the claimed design is opaque while the bottom layer of the claimed design is translucent.