Crossover Stock
"The Breech-loader and How To Use It" 1892 by William Wellington Greener
At the 1851 Great London Exhibition, James Fairman, 68 Jermyn Street showed a "Double cross-eyed gun, for gentlemen who have lost their right eye, to be used from the right shoulder and left eye."
Not a new concept. Heinrich Ebert, Wien/Vienna, c. 1820-1837
Modern Browning
Clyde Baker "Modern Gunsmithing", 1928