The piece looks like a hole was cut out of a piece of heavy stock.
To avoid irregular edge , a plunge cut ( two in this case) was made and then the circle cut out.
If the marked line for the circle was heated till molten ,with torch and then hit with air to cut ,an irregular edge would result from blowing a hole through stock. If cut with a laser , or water, or plasma cutter , still for accuracy the plunge cut away from accuracy needed line first.
I'm not saying it was cut with a plasma cutter, but ...it has very consistent edges like it could have been.
(Edit ,remove mention of torch cutting lead,melting it would be a better description.)