It looks like 440 grade stainless and is non-magnetic. It tried with a very strong Neodymium magnet. Also most mash tuns i’ve seen are either made from a cooler, copper or stainless pot and stirred with a motor in the lid, if they are stirred at all, usually just the sparging arm rotates. I don't think I’ve ever seen one with a magnetic stirrer not even sure how that would work through the grains.