It seems to have been fitted with a polarizing filter. The dirt on it makes it hard to see through.
A small telescope covered in vile substance.
This is one of the puzzle items of the "Happy Birthday" test concocted by Lucas. However, you need clean the telescope before you can see through it. In order to do this, you need to stand in the space between the Party Room and the Cake Room that triggers the automatic shower mechanism and equip the telescope to allow the water to clean the lens. Once it is clean it becomes the Telescope.