I have Darnell's A4 in my database. Unfortunately I captured it before i was logging the posting date so I can only guess as to when i first saw it. Nothing about the rifle seems to have changed in the interim.
As far as the sub inspectors marks are concerned A4's generally seem to have 5 whereas A3's one have 4. Occasionally a rifle will have more (7 or 8). I don't know for a fact but i suspect that some defect was noted, the rifle pulled out of line and sent back dow to be corrected and reinspected at each station.
On the hand-cut bolt notches. This operation may well have been by an operator using power tools. As time went on the smart thing to do would be to have the stock subcontractor do the bolt notch in their facility.
In any case it was and is a very nice example of an A4
Regards,
Jim