Um, with a fresh set of rested eyes the repair date is March 1928. So to date it before that would require the original set of touchmarks or a patent for the mechanical contrivance. Some German mechanic in the U.S. of A. can fit a proper buttplate. New England Custom Gun Service is just one such concern.

Value, not a whole lot but it deserves so much more with all the moving components....

Serbus,

Raimey
rse