Nikon MXB22255 or possibly MXB22264 LED Cluster for High Magnification Lenses. The product is intended to replace the original LED module on the Nikon 55i Eclipse Microscope.  The original 55I model did not produce enough light at magnification ranges from 40X through 100X.

Limited  availability from Nikon, as Nikon has apparently changed the item to part number 2S008-010 (LED Board with LED Light Cluster, list price $549.00.)