The General Motors roller-press trial pieces. These were struck by General Motors Technical Center in Warren Michigan to test a new coin press. The dies were made at the mint using fantasy dies as the mint would not allow real production dies to be used.
The coins, struck in copper, have control numbers and control codes L, M, or R on them signifying left, middle or right suggesting that the roller-press dies were mounted in rows of 3.
The press apparently failed to meet expectations.
General Motors apparently developed at least 2 designs of their own using a Lincoln obverse motif, P4055 and P4056.
For more information on these, see Pollock pages 431-432.