It is most interesting that this AAHE has the concave ramp spoken of, but also has a shallow notch plainly visible on the ramp. While I tend to agree on the later installation
of the rib, it does make it interesting that it was marked "Peerless Steel"-CT. and still
retained the notched ramp. Perhaps they treated this Parker slightly different due to grade and date it arrived for service. They also may have compromised similar to the catalog paragraph " fitted to finished guns". The Parker Bros catalog mentions the concave top rib.
The change in stock dimensions due to this work may have influenced the order of the additional stock and larger BT forend. Would really like to view that service work card
that is now long gone.
Some Parker Bros specialized craftsmen definitely spent time at Ilion.