I'm working to repurpose the trackball assembly of a Logitech Trackman wired mouse for use in an experimental rig. I assumed that Logitech would use Avago's ADNS series of optical flow sensors, but it doesn't appear that way. I've managed to carefully disassemble down to the sensor, but still can't find a part number. One side of the chip reads "M8aSN" but this returned nothing from Google. The sensor assembly had 6 leads running to a PIC, while the sensor itself has four pins.
I'm hoping that some sleuths here might have some ideas. Thanks in advance.
Logitech mouse specs: https://support.logitech.com/en_us/product/trackman-marble/specs
Avago ADNS series sensors (seemingly not what I'm looking at due to the difference in pin-out) [PDF!]: http://media.digikey.com/PDF/Data%20Sheets/Avago%20PDFs/ToolKitSelectionGuide.pdf
Lastly, here is the most similar-looking component I've been able to find so far. It has four pins though it is surface-mount: https://www.vishay.com/ppg?84286
Photos of what I've got: