Vintage Metal ( Cast Iron? ) Trivet

Assuming it's cast iron, but could be wrong. Cast aluminum? It's is a heavy piece APPROXIMATE MEASUREMENTS 6 & 3/4 IN DIAMETER 1 & 1/2 INCHES TALL GREAT VINTAGE CONDITION. THERE IS A SMALL DISCOLORATION SPOT ON BOTTOM EDGE OF EACH FOOT. I HAVE NOT TRIED CLEANING THIS.