The ornamental design for a back layer of a breast prosthesis, as shown and described.
FIG. 1 is a rear plan view of a back layer of a breast prosthesis, the opposite side being a mirror image thereof.
FIG. 2 is a cross sectional view thereof, taken along line 2-2 in FIG. 1; and,
FIG. 3 is a perspective view thereof.
The broken line showing is included for the purpose of illustrating environment and forms no part of the claimed design.
The stippling used in the figures represents reflective flakes dispersed through and suspended in a transparent substance that forms the back layer of a breast prosthesis and that is viewable through a rear-most transparent film of the back layer of the breast prosthesis.