As a corollary, at the turn-of-the-century many doubles were bored cylinder and full. This is the 1900 Sears catalog, with a Folsom hammer double with Twist barrels "Bored For Nitro Powder"



By the 1908 Sears catalog, Folsom's and all the other U.S. maker's doubles (if specified) were listed as 'choke bored'



I've also had several pre-1910 U.S. doubles bored right .005- .007 and left .030 - .040

https://sites.google.com/a/damascusknowledge.com/www/home