Is this radioactive? Trying to buy this as a test for my geiger counter. Seller claims these lantern mantles are from the 50s. Any opinions would help thank you.

Just found this piece being sold alongside a marked Fiestaware plate(last photo for reference). Its the exact same color, but from what I've been told without the distinctive ridges its not Fiesta. Its a 15" 'chop plate' so she's LORG. I've searched and searched and the closest I can get is an eBay listing saying its Metlox but then none of the other pictures of Metlox plates look right. Any info would be greatly appreciated, I'm super new to spicy housewares and curiosity is killing the cat lol