Parker Hale sporter?

[vintage hunter]

that's the machined depression the pad goes in.

Jim, that depression is found on all? Brit and U.S. made No.4's. Part of the manufacturing process I reckon. The milled ''window' the pad fit into would be very distinct with the pad removed if this were a T. It's pretty hard to see otherwise but you can just make out part of it around the bottom of the pad on this rifle. And it's obvious the screw holes should be inline, not diagonal.