Realistically, it could be many things. It appears to be some kind of thin film device coated in epoxy. I have precision resistor networks that look similar and I have NICAM filters that look similar. The only way you will find out is to trace the schematic of the board or remove it and dissolve the epoxy coating.
It certainly doesn't look like something "off the shelf", it will be custom made for the product it is installed into.