[Al Skierkiewicz]

All of those things would point to micro adjustments for aiming. (moving the black tube inside the larger tube. The slot would seem to me an indication that this assy would be interchangeable with another similar device. Perhaps different wavelength emmissions. The foam may be a holdover from some temperature control insulation. I am surprised that there is no power supply. That type of connector is not used for high voltage, the insulation has a low breakdown voltage.