B. Dudley,
Now you really have my interest.I checked the whole thread it it was not said anywhere that the rifle was a 30-06.It is highly possible that the rifle was imported into the US, pre WW1.A couple hints at this are the markings 30.USA 1906, and Prussia."Prussia" was usually marked on guns for export(not just to US)but not so much for domestic use. Is there a name on the recoil pad?I am interested in this because I have an Oberndorf Mauser 30-06 ca 1912, with a homemade butt plate with a 13"length of pull.This seems that a recoil pad was installed, and I wondered what type pad would be contempory. Mine also has a Lyman 35 sight and I wondered if they were avaliable at the time; and here is another one from the same period.At least yours hasn't been drilled and tapped, as mine has. You have a very nice rifle.
Mike
