When a company sets up to run a new hot stamp order they run the stamp on a few blanks 1st. Sometimes they will run it over an existing hot stamp and there will be 2 sometimes 3 different on one chip. Sometimes they will overstamp the test chips with a cancelation like you see on Michael's chip.
They throw them on the floor and sweep them up.
Sometimes the floor sweepings were sold retail as home game chips.