Cap with indicating means for distinguishing like bottles

The invention disclosed is a cap 100 with indicating means for distinguishing like bottles 150. The cap 100 comprises a first member 110 and a second member 130, the cap 100 having a first configuration in which the first and second members 110, 130 are rotatably connected, and a second configuration in which the first and second members 110, 130 are fixed to each other. The second configuration is irreversible such that the cap 100 cannot be reverted to the first configuration without the aid of tools, breaking the cap 100, or causing the cap 100 to lose functionality. Preferably the second member 130 further comprises a plurality of indicia 142, and the primary member 110 an aperture 112 through which the indicia 142 may be seen. By rotating the second member 130 and securing it to the first member 110 an indicum 142 is selected, and the cap 100 distinguished from others.