This is the first reference I could find in Greener's books; "a dummy try gun"
The Breechloader and How to Use It, 1893
https://books.google.com/books?id=LdE1AAAAMAAJ&pg=PA94&vq

No mention in The Gun and Its Development: With Notes on Shooting 1885
http://books.google.com/books?id=LAsAAAAAQAAJ

nor in Modern Shotguns 1891
http://books.google.com/books?id=FW8CAAAAYAAJ