I've posted before about 001173 but thought I'd update the info I've found out about the rifle. 001173 was indeed a receiver sent to the armorers at the AMTU at Ft. Benning. This was confirmed by Elmer Balance yesterday while he inspected my rifle. He was unable to determine whom at the AMTU built the rifle. It is my belief that the rifle was built by Hook Boutin as the Op Rod stabilizer is unique and of his own design. Anyway 001173 can be added as a loose receiver sent to Ft. Benning.