Nikon Chroma AQUA fluorescent microscope filter cube. Chroma made the filter but it is in an original Nikon filter cube holder. The Chroma number is 12331 and it will fit the NIkon  E400/600/800 and TE200/300 series of Eclipse microscopes. It comes in an original plastic filter cube case which is not pictured.

The Nikon Fluorescence Cube HC-mFISH Sp. Aqua offered here is intended for multicolor Fluorescence in situ hybridization applications.