If you purchased a Motion Sensor from SimpliSafe or an authorized retailer prior to April 2023, it is likely that you have the first generation of the Motion Sensor. 

You can also tell which version of the Motion Sensor you have by comparing the size of the dome on it. The Motion Sensor Gen 1 has a dome with a 1-inch diameter, while the Motion Sensor Gen 2 has a dome that is approximately 1 ½ inches. 

See the photo below for a side-by-side comparison between the two Motion Sensors.