Looks like a post 1912 Greifeldt offering in 20 bore over 6.3X52R/25-35 Winchester with the bullet type & weight on side of tube. Difficult to tell for sure but the lower tube looks to have the S in a Chevron noting the Schilling forge while the scattergun tubes have the K in a Rhombus/Boxed Ks as Baumgarten might but it noting a K forge. RM tubefitter & I'm sure there ar other touchmarks. What's on the frame?

Kind Regards,

Raimey
rse