The Monopeian in Greener, "The Gun", 1907
https://books.google.com/books?id=3HMCAAAAYAAJ&pg=PA412



Popular Mechanics April, 1951
https://books.google.com/books?id=AdkDAAAAMBAJ&pg=PA256&lpg



Lots of variants since to enable shooting from the right shoulder but with the left eye.

Carey Sidesighter