Superior Stainless USA by International - How old?

I found a large spoon during the excavation work at my family's farm in PA. It has the backstamp Superior Stainless USA and I think it is the INS150 pattern. Does anyone have any idea how old this piece is? I found it on a hillside that was being cleared which is nearly a quarter mile away from the properties original farmhouse. My grandparents have been here for 70 years. Noone knows exactly how old the farmhouse is, but we have found newspaper insulation that dated back to the 1840's. Any info would be great!