The lid is the same as the other cover next to it, but different in the number of lift handles, and its size
According to information from Helene, the use of the lid is for drainage
GS - Spheroidal graphite cast iron - a special cast iron in which the crystallization of carbon has been slowed down, which makes it close to steel - also called ductile iron (Thanks to Vuori Susi for the clarification)