Harry Howland of Ithaca Gun Co. applied for a patent of the Miller copy "Ithaca Selective Single Trigger" in June 1928 and was granted Ptd.# 1,818,852 Aug. 11 1931; and a non-selective trigger Pat #1,889,049 in 1932 and #1,987,402 in 1935.
Infallible
Pics of several single trigger variants are here, along with one not yet IDd
http://www.picturetrail.com/sfx/album/view/22972484