Boxhead, neat piece! I have never seen a front sight like that. Not that I am versed in the old Mausers but that one seems very different.
I have pictures of only one old Mauser from the early 1900's at home. Mr. Fossum had one. They left Bergen country in 1913 if memory serves for southern Alberta. Don't know of any other boltguns at home until the 30's....yet. This picture is from between 1910and 1912 as the rifle on the far left was built 1911 and came to Alberta the same year. Fossums rifle has the raised face on the stock just like your Whelan.
If anyone else has some old Mausers to share feel free to post them.