The earliest mention I've run across of the "pigeon gun" is in an article titled: "The Sportsmen's Exposition of 1897" that was printed in the April, 1897 edition of Sportsman's Magazine. I've got a copy of the Baker portion of the article along with other "clippings" about Baker here:

https://sites.google.com/site/bakerguns/home/baker-clippings


The author references Baker's asking price as $80