Did you see, as disston and Otg alluded to, that it has "
American Lead" and "
Indianapolis" embossed on it? It is almost certainly a plug ingot from the American Lead Corporation, which was located in the heart of the historic Martindale-Brightwood section of Indianapolis. From the 40's to the 60's, the American Lead Corporation operated a lead reclamation smelter there. That means they took in stuff that had lead in it (i.e., old batteries, etc), combined it with other compounds, melted it at high heat, and used other processes and equipment to separate the lead, poured into ingots for sale.
Infamous EPA site. Read more
here and
here.
Was your great great great uncle a plumber? Lead ingots came and still come in sheets, bars, and round plugs, like that one. The round plugs were usually used by plumbers. Sometimes they came in a chain, connected by a thin strand of lead. The plumber would snap one off at a time as needed.
Ironically, secondary lead smelting is a revived business in many areas of the United States today, due in no small part to the proliferation of rifle ranges. They are routinely excavated and the soil sent to secondary smelters, which now operate with regulations and safer practices and processes.
