Industrial Metal Mittin Mold circa 1940

The day was spent at my wife’s Vassar mini reunion group. It was an interesting day with lunch at Greens’s and a trip to the SF Antiques Fair. The fair featured high end items from all over the country and some from the UK. What caught my eye was this mold. No one in the group had any idea what it was used for and a google search didn’t provide any answers either. Can anyone out there help?