McPhail:

Does either of the doubles you mentioned have the wide/Lindner type forend lug? If indeed of German origin the "A.S." would have been for August Schuler.

Frederick Schilling of St. Louis worked with or joined Johann Blickensdorfer in the late 1860s and I think they parted ways in the mid 1870s.

Kind Regards,

Raimey
rse