John I believe the pads may have been introduced earlier. I have a late 1st block rifle (3423505) which I believe has the pad. I'll take it apart tomorrow and confirm.
The rifle has no indications of an overhaul.
Regards,
Jim
As I thought the above captioned rifle is equipped with a pad. Aug 43 bbl. Assembled and shipped in Oct/Nov 43.
All indications lead me to believe the rifle is as issued save the scope and rings which I added.