S.L.A.T. - Sinalização Luminosa Automática de Trânsito - Automatic Traffic Light Signaling CML - Câmara Municipal de Lisboa - Lisbon Municipality
GJS-500 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.
The lid is similar to another cover made by the same manufacturer