The lid is similar to another manhole cover made by the same manufacturer
LÅS - lock
The yellow ring is intended for quick identification of the type of cover (especially in cases of snow covering part of the cover), and means a general cover (without a defined purpose).
Note that the outer ring was made by another manufacturer (ULEFOS).
GJS-500-7 also called GGG50 marks a strong and heat-resistant type of metal while GJS is a sign for Continuously Cast Spheroidal Graphite Iron - which describes a process in which the metal is continuously fed.