The cell is used for electrochemical measurement of samples on a transparent substrate. A sample is placed under the fused silica window, with substrate facing the window, so it has contact with electrolyte inside the cell. Four identical holes around the window holder are compatible with cage system from Thorlabs. They can be used to mount the cell to light sources like a photoelectric spectrometer in such a way so the light penetrates the substrate.
We usually modify this design to a particular experimental requirements.