Looks to be a blitz or trigger-plate action or one of those odd round action variants and I wonder if the 1908 refers to the number made on that action rather than the date. With the Nitro stamp it would date to post 1912.

http://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=261603&page=1
Sauer Round Action variant but not our bird.

Kind Regards,

Raimey
rse