This is a 2 piece printed housing to replace the original housing supplied with the sensor. The intent was to have something that was easier to put the sensor on, had more airflow, more protection, a little more appropriate sun shading (the vents and Stevenson style screen) to get more accurate temps.
Save one of the screws that comes with the sensor; that's what you'll use to secure the sensor to this housing.
The author marked this model as their own original creation.